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cosmopolitan/third_party/sqlite3/btree.c
Justine Tunney 5144c22189 Add test for ioctl(SIOCGIFCONF) and polyfill on BSDs 
- Use nullness checks when calling weakly linked functions.

- Avoid typedef for reasons described in Linux Kernel style guide.

- Avoid enum in in Windows headers. Earlier in Cosmo's history all one
  hundred files in libc/nt/enum/ used to be enums and it resulted in
  gigabytes of DWARF data almost as large as everything else in the
  codebase combined.

- Bitfields aren't our friends. They have frequent ABI breakages,
  inconsistent arithmetic across compilers, and different endianness
  between cpus. Compiler authors also haven't invested much roi into
  making bit fields go fast so they produce poor assembly.

- Use memccpy() instead of strncpy() or snprintf() for length-bounded
  copying of C strings. strncpy() is a misunderstood function and
  snprintf() is awesome but memccpy() deserves more love.
2021-06-25 18:44:04 -07:00

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/*
** 2004 April 6
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements an external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "third_party/sqlite3/btreeInt.inc"
#if defined(__GNUC__) && !defined(__llvm__)
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif
/* clang-format off */
/*
** The header string that appears at the beginning of every
** SQLite database.
*/
static const char zMagicHeader[] = SQLITE_FILE_HEADER;
/*
** Set this global variable to 1 to enable tracing using the TRACE
** macro.
*/
#if 0
int sqlite3BtreeTrace=1; /* True to enable tracing */
# define TRACE(X) if(sqlite3BtreeTrace){printf X;fflush(stdout);}
#else
# define TRACE(X)
#endif
/*
** Extract a 2-byte big-endian integer from an array of unsigned bytes.
** But if the value is zero, make it 65536.
**
** This routine is used to extract the "offset to cell content area" value
** from the header of a btree page. If the page size is 65536 and the page
** is empty, the offset should be 65536, but the 2-byte value stores zero.
** This routine makes the necessary adjustment to 65536.
*/
#define get2byteNotZero(X) (((((int)get2byte(X))-1)&0xffff)+1)
/*
** Values passed as the 5th argument to allocateBtreePage()
*/
#define BTALLOC_ANY 0 /* Allocate any page */
#define BTALLOC_EXACT 1 /* Allocate exact page if possible */
#define BTALLOC_LE 2 /* Allocate any page <= the parameter */
/*
** Macro IfNotOmitAV(x) returns (x) if SQLITE_OMIT_AUTOVACUUM is not
** defined, or 0 if it is. For example:
**
** bIncrVacuum = IfNotOmitAV(pBtShared->incrVacuum);
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
#define IfNotOmitAV(expr) (expr)
#else
#define IfNotOmitAV(expr) 0
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** A list of BtShared objects that are eligible for participation
** in shared cache. This variable has file scope during normal builds,
** but the test harness needs to access it so we make it global for
** test builds.
**
** Access to this variable is protected by SQLITE_MUTEX_STATIC_MAIN.
*/
#ifdef SQLITE_TEST
BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
#else
static BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
#endif
#endif /* SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Enable or disable the shared pager and schema features.
**
** This routine has no effect on existing database connections.
** The shared cache setting effects only future calls to
** sqlite3_open(), sqlite3_open16(), or sqlite3_open_v2().
*/
int sqlite3_enable_shared_cache(int enable){
sqlite3GlobalConfig.sharedCacheEnabled = enable;
return SQLITE_OK;
}
#endif
#ifdef SQLITE_OMIT_SHARED_CACHE
/*
** The functions querySharedCacheTableLock(), setSharedCacheTableLock(),
** and clearAllSharedCacheTableLocks()
** manipulate entries in the BtShared.pLock linked list used to store
** shared-cache table level locks. If the library is compiled with the
** shared-cache feature disabled, then there is only ever one user
** of each BtShared structure and so this locking is not necessary.
** So define the lock related functions as no-ops.
*/
#define querySharedCacheTableLock(a,b,c) SQLITE_OK
#define setSharedCacheTableLock(a,b,c) SQLITE_OK
#define clearAllSharedCacheTableLocks(a)
#define downgradeAllSharedCacheTableLocks(a)
#define hasSharedCacheTableLock(a,b,c,d) 1
#define hasReadConflicts(a, b) 0
#endif
#ifdef SQLITE_DEBUG
/*
** Return and reset the seek counter for a Btree object.
*/
sqlite3_uint64 sqlite3BtreeSeekCount(Btree *pBt){
u64 n = pBt->nSeek;
pBt->nSeek = 0;
return n;
}
#endif
/*
** Implementation of the SQLITE_CORRUPT_PAGE() macro. Takes a single
** (MemPage*) as an argument. The (MemPage*) must not be NULL.
**
** If SQLITE_DEBUG is not defined, then this macro is equivalent to
** SQLITE_CORRUPT_BKPT. Or, if SQLITE_DEBUG is set, then the log message
** normally produced as a side-effect of SQLITE_CORRUPT_BKPT is augmented
** with the page number and filename associated with the (MemPage*).
*/
#ifdef SQLITE_DEBUG
int corruptPageError(int lineno, MemPage *p){
char *zMsg;
sqlite3BeginBenignMalloc();
zMsg = sqlite3_mprintf("database corruption page %d of %s",
(int)p->pgno, sqlite3PagerFilename(p->pBt->pPager, 0)
);
sqlite3EndBenignMalloc();
if( zMsg ){
sqlite3ReportError(SQLITE_CORRUPT, lineno, zMsg);
}
sqlite3_free(zMsg);
return SQLITE_CORRUPT_BKPT;
}
# define SQLITE_CORRUPT_PAGE(pMemPage) corruptPageError(__LINE__, pMemPage)
#else
# define SQLITE_CORRUPT_PAGE(pMemPage) SQLITE_CORRUPT_PGNO(pMemPage->pgno)
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
#ifdef SQLITE_DEBUG
/*
**** This function is only used as part of an assert() statement. ***
**
** Check to see if pBtree holds the required locks to read or write to the
** table with root page iRoot. Return 1 if it does and 0 if not.
**
** For example, when writing to a table with root-page iRoot via
** Btree connection pBtree:
**
** assert( hasSharedCacheTableLock(pBtree, iRoot, 0, WRITE_LOCK) );
**
** When writing to an index that resides in a sharable database, the
** caller should have first obtained a lock specifying the root page of
** the corresponding table. This makes things a bit more complicated,
** as this module treats each table as a separate structure. To determine
** the table corresponding to the index being written, this
** function has to search through the database schema.
**
** Instead of a lock on the table/index rooted at page iRoot, the caller may
** hold a write-lock on the schema table (root page 1). This is also
** acceptable.
*/
static int hasSharedCacheTableLock(
Btree *pBtree, /* Handle that must hold lock */
Pgno iRoot, /* Root page of b-tree */
int isIndex, /* True if iRoot is the root of an index b-tree */
int eLockType /* Required lock type (READ_LOCK or WRITE_LOCK) */
){
Schema *pSchema = (Schema *)pBtree->pBt->pSchema;
Pgno iTab = 0;
BtLock *pLock;
/* If this database is not shareable, or if the client is reading
** and has the read-uncommitted flag set, then no lock is required.
** Return true immediately.
*/
if( (pBtree->sharable==0)
|| (eLockType==READ_LOCK && (pBtree->db->flags & SQLITE_ReadUncommit))
){
return 1;
}
/* If the client is reading or writing an index and the schema is
** not loaded, then it is too difficult to actually check to see if
** the correct locks are held. So do not bother - just return true.
** This case does not come up very often anyhow.
*/
if( isIndex && (!pSchema || (pSchema->schemaFlags&DB_SchemaLoaded)==0) ){
return 1;
}
/* Figure out the root-page that the lock should be held on. For table
** b-trees, this is just the root page of the b-tree being read or
** written. For index b-trees, it is the root page of the associated
** table. */
if( isIndex ){
HashElem *p;
int bSeen = 0;
for(p=sqliteHashFirst(&pSchema->idxHash); p; p=sqliteHashNext(p)){
Index *pIdx = (Index *)sqliteHashData(p);
if( pIdx->tnum==(int)iRoot ){
if( bSeen ){
/* Two or more indexes share the same root page. There must
** be imposter tables. So just return true. The assert is not
** useful in that case. */
return 1;
}
iTab = pIdx->pTable->tnum;
bSeen = 1;
}
}
}else{
iTab = iRoot;
}
/* Search for the required lock. Either a write-lock on root-page iTab, a
** write-lock on the schema table, or (if the client is reading) a
** read-lock on iTab will suffice. Return 1 if any of these are found. */
for(pLock=pBtree->pBt->pLock; pLock; pLock=pLock->pNext){
if( pLock->pBtree==pBtree
&& (pLock->iTable==iTab || (pLock->eLock==WRITE_LOCK && pLock->iTable==1))
&& pLock->eLock>=eLockType
){
return 1;
}
}
/* Failed to find the required lock. */
return 0;
}
#endif /* SQLITE_DEBUG */
#ifdef SQLITE_DEBUG
/*
**** This function may be used as part of assert() statements only. ****
**
** Return true if it would be illegal for pBtree to write into the
** table or index rooted at iRoot because other shared connections are
** simultaneously reading that same table or index.
**
** It is illegal for pBtree to write if some other Btree object that
** shares the same BtShared object is currently reading or writing
** the iRoot table. Except, if the other Btree object has the
** read-uncommitted flag set, then it is OK for the other object to
** have a read cursor.
**
** For example, before writing to any part of the table or index
** rooted at page iRoot, one should call:
**
** assert( !hasReadConflicts(pBtree, iRoot) );
*/
static int hasReadConflicts(Btree *pBtree, Pgno iRoot){
BtCursor *p;
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
if( p->pgnoRoot==iRoot
&& p->pBtree!=pBtree
&& 0==(p->pBtree->db->flags & SQLITE_ReadUncommit)
){
return 1;
}
}
return 0;
}
#endif /* #ifdef SQLITE_DEBUG */
/*
** Query to see if Btree handle p may obtain a lock of type eLock
** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
** SQLITE_OK if the lock may be obtained (by calling
** setSharedCacheTableLock()), or SQLITE_LOCKED if not.
*/
static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
assert( p->db!=0 );
assert( !(p->db->flags&SQLITE_ReadUncommit)||eLock==WRITE_LOCK||iTab==1 );
/* If requesting a write-lock, then the Btree must have an open write
** transaction on this file. And, obviously, for this to be so there
** must be an open write transaction on the file itself.
*/
assert( eLock==READ_LOCK || (p==pBt->pWriter && p->inTrans==TRANS_WRITE) );
assert( eLock==READ_LOCK || pBt->inTransaction==TRANS_WRITE );
/* This routine is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
/* If some other connection is holding an exclusive lock, the
** requested lock may not be obtained.
*/
if( pBt->pWriter!=p && (pBt->btsFlags & BTS_EXCLUSIVE)!=0 ){
sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
return SQLITE_LOCKED_SHAREDCACHE;
}
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
/* The condition (pIter->eLock!=eLock) in the following if(...)
** statement is a simplification of:
**
** (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
**
** since we know that if eLock==WRITE_LOCK, then no other connection
** may hold a WRITE_LOCK on any table in this file (since there can
** only be a single writer).
*/
assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
if( eLock==WRITE_LOCK ){
assert( p==pBt->pWriter );
pBt->btsFlags |= BTS_PENDING;
}
return SQLITE_LOCKED_SHAREDCACHE;
}
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Add a lock on the table with root-page iTable to the shared-btree used
** by Btree handle p. Parameter eLock must be either READ_LOCK or
** WRITE_LOCK.
**
** This function assumes the following:
**
** (a) The specified Btree object p is connected to a sharable
** database (one with the BtShared.sharable flag set), and
**
** (b) No other Btree objects hold a lock that conflicts
** with the requested lock (i.e. querySharedCacheTableLock() has
** already been called and returned SQLITE_OK).
**
** SQLITE_OK is returned if the lock is added successfully. SQLITE_NOMEM
** is returned if a malloc attempt fails.
*/
static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pLock = 0;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
assert( p->db!=0 );
/* A connection with the read-uncommitted flag set will never try to
** obtain a read-lock using this function. The only read-lock obtained
** by a connection in read-uncommitted mode is on the sqlite_schema
** table, and that lock is obtained in BtreeBeginTrans(). */
assert( 0==(p->db->flags&SQLITE_ReadUncommit) || eLock==WRITE_LOCK );
/* This function should only be called on a sharable b-tree after it
** has been determined that no other b-tree holds a conflicting lock. */
assert( p->sharable );
assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );
/* First search the list for an existing lock on this table. */
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->iTable==iTable && pIter->pBtree==p ){
pLock = pIter;
break;
}
}
/* If the above search did not find a BtLock struct associating Btree p
** with table iTable, allocate one and link it into the list.
*/
if( !pLock ){
pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
if( !pLock ){
return SQLITE_NOMEM_BKPT;
}
pLock->iTable = iTable;
pLock->pBtree = p;
pLock->pNext = pBt->pLock;
pBt->pLock = pLock;
}
/* Set the BtLock.eLock variable to the maximum of the current lock
** and the requested lock. This means if a write-lock was already held
** and a read-lock requested, we don't incorrectly downgrade the lock.
*/
assert( WRITE_LOCK>READ_LOCK );
if( eLock>pLock->eLock ){
pLock->eLock = eLock;
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Release all the table locks (locks obtained via calls to
** the setSharedCacheTableLock() procedure) held by Btree object p.
**
** This function assumes that Btree p has an open read or write
** transaction. If it does not, then the BTS_PENDING flag
** may be incorrectly cleared.
*/
static void clearAllSharedCacheTableLocks(Btree *p){
BtShared *pBt = p->pBt;
BtLock **ppIter = &pBt->pLock;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->sharable || 0==*ppIter );
assert( p->inTrans>0 );
while( *ppIter ){
BtLock *pLock = *ppIter;
assert( (pBt->btsFlags & BTS_EXCLUSIVE)==0 || pBt->pWriter==pLock->pBtree );
assert( pLock->pBtree->inTrans>=pLock->eLock );
if( pLock->pBtree==p ){
*ppIter = pLock->pNext;
assert( pLock->iTable!=1 || pLock==&p->lock );
if( pLock->iTable!=1 ){
sqlite3_free(pLock);
}
}else{
ppIter = &pLock->pNext;
}
}
assert( (pBt->btsFlags & BTS_PENDING)==0 || pBt->pWriter );
if( pBt->pWriter==p ){
pBt->pWriter = 0;
pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
}else if( pBt->nTransaction==2 ){
/* This function is called when Btree p is concluding its
** transaction. If there currently exists a writer, and p is not
** that writer, then the number of locks held by connections other
** than the writer must be about to drop to zero. In this case
** set the BTS_PENDING flag to 0.
**
** If there is not currently a writer, then BTS_PENDING must
** be zero already. So this next line is harmless in that case.
*/
pBt->btsFlags &= ~BTS_PENDING;
}
}
/*
** This function changes all write-locks held by Btree p into read-locks.
*/
static void downgradeAllSharedCacheTableLocks(Btree *p){
BtShared *pBt = p->pBt;
if( pBt->pWriter==p ){
BtLock *pLock;
pBt->pWriter = 0;
pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
for(pLock=pBt->pLock; pLock; pLock=pLock->pNext){
assert( pLock->eLock==READ_LOCK || pLock->pBtree==p );
pLock->eLock = READ_LOCK;
}
}
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
static void releasePage(MemPage *pPage); /* Forward reference */
static void releasePageOne(MemPage *pPage); /* Forward reference */
static void releasePageNotNull(MemPage *pPage); /* Forward reference */
/*
***** This routine is used inside of assert() only ****
**
** Verify that the cursor holds the mutex on its BtShared
*/
#ifdef SQLITE_DEBUG
static int cursorHoldsMutex(BtCursor *p){
return sqlite3_mutex_held(p->pBt->mutex);
}
/* Verify that the cursor and the BtShared agree about what is the current
** database connetion. This is important in shared-cache mode. If the database
** connection pointers get out-of-sync, it is possible for routines like
** btreeInitPage() to reference an stale connection pointer that references a
** a connection that has already closed. This routine is used inside assert()
** statements only and for the purpose of double-checking that the btree code
** does keep the database connection pointers up-to-date.
*/
static int cursorOwnsBtShared(BtCursor *p){
assert( cursorHoldsMutex(p) );
return (p->pBtree->db==p->pBt->db);
}
#endif
/*
** Invalidate the overflow cache of the cursor passed as the first argument.
** on the shared btree structure pBt.
*/
#define invalidateOverflowCache(pCur) (pCur->curFlags &= ~BTCF_ValidOvfl)
/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
for(p=pBt->pCursor; p; p=p->pNext){
invalidateOverflowCache(p);
}
}
#ifndef SQLITE_OMIT_INCRBLOB
/*
** This function is called before modifying the contents of a table
** to invalidate any incrblob cursors that are open on the
** row or one of the rows being modified.
**
** If argument isClearTable is true, then the entire contents of the
** table is about to be deleted. In this case invalidate all incrblob
** cursors open on any row within the table with root-page pgnoRoot.
**
** Otherwise, if argument isClearTable is false, then the row with
** rowid iRow is being replaced or deleted. In this case invalidate
** only those incrblob cursors open on that specific row.
*/
static void invalidateIncrblobCursors(
Btree *pBtree, /* The database file to check */
Pgno pgnoRoot, /* The table that might be changing */
i64 iRow, /* The rowid that might be changing */
int isClearTable /* True if all rows are being deleted */
){
BtCursor *p;
if( pBtree->hasIncrblobCur==0 ) return;
assert( sqlite3BtreeHoldsMutex(pBtree) );
pBtree->hasIncrblobCur = 0;
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
if( (p->curFlags & BTCF_Incrblob)!=0 ){
pBtree->hasIncrblobCur = 1;
if( p->pgnoRoot==pgnoRoot && (isClearTable || p->info.nKey==iRow) ){
p->eState = CURSOR_INVALID;
}
}
}
}
#else
/* Stub function when INCRBLOB is omitted */
#define invalidateIncrblobCursors(w,x,y,z)
#endif /* SQLITE_OMIT_INCRBLOB */
/*
** Set bit pgno of the BtShared.pHasContent bitvec. This is called
** when a page that previously contained data becomes a free-list leaf
** page.
**
** The BtShared.pHasContent bitvec exists to work around an obscure
** bug caused by the interaction of two useful IO optimizations surrounding
** free-list leaf pages:
**
** 1) When all data is deleted from a page and the page becomes
** a free-list leaf page, the page is not written to the database
** (as free-list leaf pages contain no meaningful data). Sometimes
** such a page is not even journalled (as it will not be modified,
** why bother journalling it?).
**
** 2) When a free-list leaf page is reused, its content is not read
** from the database or written to the journal file (why should it
** be, if it is not at all meaningful?).
**
** By themselves, these optimizations work fine and provide a handy
** performance boost to bulk delete or insert operations. However, if
** a page is moved to the free-list and then reused within the same
** transaction, a problem comes up. If the page is not journalled when
** it is moved to the free-list and it is also not journalled when it
** is extracted from the free-list and reused, then the original data
** may be lost. In the event of a rollback, it may not be possible
** to restore the database to its original configuration.
**
** The solution is the BtShared.pHasContent bitvec. Whenever a page is
** moved to become a free-list leaf page, the corresponding bit is
** set in the bitvec. Whenever a leaf page is extracted from the free-list,
** optimization 2 above is omitted if the corresponding bit is already
** set in BtShared.pHasContent. The contents of the bitvec are cleared
** at the end of every transaction.
*/
static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
int rc = SQLITE_OK;
if( !pBt->pHasContent ){
assert( pgno<=pBt->nPage );
pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
if( !pBt->pHasContent ){
rc = SQLITE_NOMEM_BKPT;
}
}
if( rc==SQLITE_OK && pgno<=sqlite3BitvecSize(pBt->pHasContent) ){
rc = sqlite3BitvecSet(pBt->pHasContent, pgno);
}
return rc;
}
/*
** Query the BtShared.pHasContent vector.
**
** This function is called when a free-list leaf page is removed from the
** free-list for reuse. It returns false if it is safe to retrieve the
** page from the pager layer with the 'no-content' flag set. True otherwise.
*/
static int btreeGetHasContent(BtShared *pBt, Pgno pgno){
Bitvec *p = pBt->pHasContent;
return p && (pgno>sqlite3BitvecSize(p) || sqlite3BitvecTestNotNull(p, pgno));
}
/*
** Clear (destroy) the BtShared.pHasContent bitvec. This should be
** invoked at the conclusion of each write-transaction.
*/
static void btreeClearHasContent(BtShared *pBt){
sqlite3BitvecDestroy(pBt->pHasContent);
pBt->pHasContent = 0;
}
/*
** Release all of the apPage[] pages for a cursor.
*/
static void btreeReleaseAllCursorPages(BtCursor *pCur){
int i;
if( pCur->iPage>=0 ){
for(i=0; i<pCur->iPage; i++){
releasePageNotNull(pCur->apPage[i]);
}
releasePageNotNull(pCur->pPage);
pCur->iPage = -1;
}
}
/*
** The cursor passed as the only argument must point to a valid entry
** when this function is called (i.e. have eState==CURSOR_VALID). This
** function saves the current cursor key in variables pCur->nKey and
** pCur->pKey. SQLITE_OK is returned if successful or an SQLite error
** code otherwise.
**
** If the cursor is open on an intkey table, then the integer key
** (the rowid) is stored in pCur->nKey and pCur->pKey is left set to
** NULL. If the cursor is open on a non-intkey table, then pCur->pKey is
** set to point to a malloced buffer pCur->nKey bytes in size containing
** the key.
*/
static int saveCursorKey(BtCursor *pCur){
int rc = SQLITE_OK;
assert( CURSOR_VALID==pCur->eState );
assert( 0==pCur->pKey );
assert( cursorHoldsMutex(pCur) );
if( pCur->curIntKey ){
/* Only the rowid is required for a table btree */
pCur->nKey = sqlite3BtreeIntegerKey(pCur);
}else{
/* For an index btree, save the complete key content. It is possible
** that the current key is corrupt. In that case, it is possible that
** the sqlite3VdbeRecordUnpack() function may overread the buffer by
** up to the size of 1 varint plus 1 8-byte value when the cursor
** position is restored. Hence the 17 bytes of padding allocated
** below. */
void *pKey;
pCur->nKey = sqlite3BtreePayloadSize(pCur);
pKey = sqlite3Malloc( pCur->nKey + 9 + 8 );
if( pKey ){
rc = sqlite3BtreePayload(pCur, 0, (int)pCur->nKey, pKey);
if( rc==SQLITE_OK ){
memset(((u8*)pKey)+pCur->nKey, 0, 9+8);
pCur->pKey = pKey;
}else{
sqlite3_free(pKey);
}
}else{
rc = SQLITE_NOMEM_BKPT;
}
}
assert( !pCur->curIntKey || !pCur->pKey );
return rc;
}
/*
** Save the current cursor position in the variables BtCursor.nKey
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
**
** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
** prior to calling this routine.
*/
static int saveCursorPosition(BtCursor *pCur){
int rc;
assert( CURSOR_VALID==pCur->eState || CURSOR_SKIPNEXT==pCur->eState );
assert( 0==pCur->pKey );
assert( cursorHoldsMutex(pCur) );
if( pCur->curFlags & BTCF_Pinned ){
return SQLITE_CONSTRAINT_PINNED;
}
if( pCur->eState==CURSOR_SKIPNEXT ){
pCur->eState = CURSOR_VALID;
}else{
pCur->skipNext = 0;
}
rc = saveCursorKey(pCur);
if( rc==SQLITE_OK ){
btreeReleaseAllCursorPages(pCur);
pCur->eState = CURSOR_REQUIRESEEK;
}
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl|BTCF_AtLast);
return rc;
}
/* Forward reference */
static int SQLITE_NOINLINE saveCursorsOnList(BtCursor*,Pgno,BtCursor*);
/*
** Save the positions of all cursors (except pExcept) that are open on
** the table with root-page iRoot. "Saving the cursor position" means that
** the location in the btree is remembered in such a way that it can be
** moved back to the same spot after the btree has been modified. This
** routine is called just before cursor pExcept is used to modify the
** table, for example in BtreeDelete() or BtreeInsert().
**
** If there are two or more cursors on the same btree, then all such
** cursors should have their BTCF_Multiple flag set. The btreeCursor()
** routine enforces that rule. This routine only needs to be called in
** the uncommon case when pExpect has the BTCF_Multiple flag set.
**
** If pExpect!=NULL and if no other cursors are found on the same root-page,
** then the BTCF_Multiple flag on pExpect is cleared, to avoid another
** pointless call to this routine.
**
** Implementation note: This routine merely checks to see if any cursors
** need to be saved. It calls out to saveCursorsOnList() in the (unusual)
** event that cursors are in need to being saved.
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pExcept==0 || pExcept->pBt==pBt );
for(p=pBt->pCursor; p; p=p->pNext){
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break;
}
if( p ) return saveCursorsOnList(p, iRoot, pExcept);
if( pExcept ) pExcept->curFlags &= ~BTCF_Multiple;
return SQLITE_OK;
}
/* This helper routine to saveAllCursors does the actual work of saving
** the cursors if and when a cursor is found that actually requires saving.
** The common case is that no cursors need to be saved, so this routine is
** broken out from its caller to avoid unnecessary stack pointer movement.
*/
static int SQLITE_NOINLINE saveCursorsOnList(
BtCursor *p, /* The first cursor that needs saving */
Pgno iRoot, /* Only save cursor with this iRoot. Save all if zero */
BtCursor *pExcept /* Do not save this cursor */
){
do{
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
int rc = saveCursorPosition(p);
if( SQLITE_OK!=rc ){
return rc;
}
}else{
testcase( p->iPage>=0 );
btreeReleaseAllCursorPages(p);
}
}
p = p->pNext;
}while( p );
return SQLITE_OK;
}
/*
** Clear the current cursor position.
*/
void sqlite3BtreeClearCursor(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
pCur->eState = CURSOR_INVALID;
}
/*
** In this version of BtreeMoveto, pKey is a packed index record
** such as is generated by the OP_MakeRecord opcode. Unpack the
** record and then call BtreeMovetoUnpacked() to do the work.
*/
static int btreeMoveto(
BtCursor *pCur, /* Cursor open on the btree to be searched */
const void *pKey, /* Packed key if the btree is an index */
i64 nKey, /* Integer key for tables. Size of pKey for indices */
int bias, /* Bias search to the high end */
int *pRes /* Write search results here */
){
int rc; /* Status code */
UnpackedRecord *pIdxKey; /* Unpacked index key */
if( pKey ){
KeyInfo *pKeyInfo = pCur->pKeyInfo;
assert( nKey==(i64)(int)nKey );
pIdxKey = sqlite3VdbeAllocUnpackedRecord(pKeyInfo);
if( pIdxKey==0 ) return SQLITE_NOMEM_BKPT;
sqlite3VdbeRecordUnpack(pKeyInfo, (int)nKey, pKey, pIdxKey);
if( pIdxKey->nField==0 || pIdxKey->nField>pKeyInfo->nAllField ){
rc = SQLITE_CORRUPT_BKPT;
goto moveto_done;
}
}else{
pIdxKey = 0;
}
rc = sqlite3BtreeMovetoUnpacked(pCur, pIdxKey, nKey, bias, pRes);
moveto_done:
if( pIdxKey ){
sqlite3DbFree(pCur->pKeyInfo->db, pIdxKey);
}
return rc;
}
/*
** Restore the cursor to the position it was in (or as close to as possible)
** when saveCursorPosition() was called. Note that this call deletes the
** saved position info stored by saveCursorPosition(), so there can be
** at most one effective restoreCursorPosition() call after each
** saveCursorPosition().
*/
static int btreeRestoreCursorPosition(BtCursor *pCur){
int rc;
int skipNext = 0;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState>=CURSOR_REQUIRESEEK );
if( pCur->eState==CURSOR_FAULT ){
return pCur->skipNext;
}
pCur->eState = CURSOR_INVALID;
if( sqlite3FaultSim(410) ){
rc = SQLITE_IOERR;
}else{
rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &skipNext);
}
if( rc==SQLITE_OK ){
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
if( skipNext ) pCur->skipNext = skipNext;
if( pCur->skipNext && pCur->eState==CURSOR_VALID ){
pCur->eState = CURSOR_SKIPNEXT;
}
}
return rc;
}
#define restoreCursorPosition(p) \
(p->eState>=CURSOR_REQUIRESEEK ? \
btreeRestoreCursorPosition(p) : \
SQLITE_OK)
/*
** Determine whether or not a cursor has moved from the position where
** it was last placed, or has been invalidated for any other reason.
** Cursors can move when the row they are pointing at is deleted out
** from under them, for example. Cursor might also move if a btree
** is rebalanced.
**
** Calling this routine with a NULL cursor pointer returns false.
**
** Use the separate sqlite3BtreeCursorRestore() routine to restore a cursor
** back to where it ought to be if this routine returns true.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur){
assert( EIGHT_BYTE_ALIGNMENT(pCur)
|| pCur==sqlite3BtreeFakeValidCursor() );
assert( offsetof(BtCursor, eState)==0 );
assert( sizeof(pCur->eState)==1 );
return CURSOR_VALID != *(u8*)pCur;
}
/*
** Return a pointer to a fake BtCursor object that will always answer
** false to the sqlite3BtreeCursorHasMoved() routine above. The fake
** cursor returned must not be used with any other Btree interface.
*/
BtCursor *sqlite3BtreeFakeValidCursor(void){
static u8 fakeCursor = CURSOR_VALID;
assert( offsetof(BtCursor, eState)==0 );
return (BtCursor*)&fakeCursor;
}
/*
** This routine restores a cursor back to its original position after it
** has been moved by some outside activity (such as a btree rebalance or
** a row having been deleted out from under the cursor).
**
** On success, the *pDifferentRow parameter is false if the cursor is left
** pointing at exactly the same row. *pDifferntRow is the row the cursor
** was pointing to has been deleted, forcing the cursor to point to some
** nearby row.
**
** This routine should only be called for a cursor that just returned
** TRUE from sqlite3BtreeCursorHasMoved().
*/
int sqlite3BtreeCursorRestore(BtCursor *pCur, int *pDifferentRow){
int rc;
assert( pCur!=0 );
assert( pCur->eState!=CURSOR_VALID );
rc = restoreCursorPosition(pCur);
if( rc ){
*pDifferentRow = 1;
return rc;
}
if( pCur->eState!=CURSOR_VALID ){
*pDifferentRow = 1;
}else{
*pDifferentRow = 0;
}
return SQLITE_OK;
}
#ifdef SQLITE_ENABLE_CURSOR_HINTS
/*
** Provide hints to the cursor. The particular hint given (and the type
** and number of the varargs parameters) is determined by the eHintType
** parameter. See the definitions of the BTREE_HINT_* macros for details.
*/
void sqlite3BtreeCursorHint(BtCursor *pCur, int eHintType, ...){
/* Used only by system that substitute their own storage engine */
}
#endif
/*
** Provide flag hints to the cursor.
*/
void sqlite3BtreeCursorHintFlags(BtCursor *pCur, unsigned x){
assert( x==BTREE_SEEK_EQ || x==BTREE_BULKLOAD || x==0 );
pCur->hints = x;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
**
** Return 0 (not a valid page) for pgno==1 since there is
** no pointer map associated with page 1. The integrity_check logic
** requires that ptrmapPageno(*,1)!=1.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
int nPagesPerMapPage;
Pgno iPtrMap, ret;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno<2 ) return 0;
nPagesPerMapPage = (pBt->usableSize/5)+1;
iPtrMap = (pgno-2)/nPagesPerMapPage;
ret = (iPtrMap*nPagesPerMapPage) + 2;
if( ret==PENDING_BYTE_PAGE(pBt) ){
ret++;
}
return ret;
}
/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
**
** If *pRC is initially non-zero (non-SQLITE_OK) then this routine is
** a no-op. If an error occurs, the appropriate error code is written
** into *pRC.
*/
static void ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent, int *pRC){
DbPage *pDbPage; /* The pointer map page */
u8 *pPtrmap; /* The pointer map data */
Pgno iPtrmap; /* The pointer map page number */
int offset; /* Offset in pointer map page */
int rc; /* Return code from subfunctions */
if( *pRC ) return;
assert( sqlite3_mutex_held(pBt->mutex) );
/* The super-journal page number must never be used as a pointer map page */
assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
assert( pBt->autoVacuum );
if( key==0 ){
*pRC = SQLITE_CORRUPT_BKPT;
return;
}
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage, 0);
if( rc!=SQLITE_OK ){
*pRC = rc;
return;
}
if( ((char*)sqlite3PagerGetExtra(pDbPage))[0]!=0 ){
/* The first byte of the extra data is the MemPage.isInit byte.
** If that byte is set, it means this page is also being used
** as a btree page. */
*pRC = SQLITE_CORRUPT_BKPT;
goto ptrmap_exit;
}
offset = PTRMAP_PTROFFSET(iPtrmap, key);
if( offset<0 ){
*pRC = SQLITE_CORRUPT_BKPT;
goto ptrmap_exit;
}
assert( offset <= (int)pBt->usableSize-5 );
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
*pRC= rc = sqlite3PagerWrite(pDbPage);
if( rc==SQLITE_OK ){
pPtrmap[offset] = eType;
put4byte(&pPtrmap[offset+1], parent);
}
}
ptrmap_exit:
sqlite3PagerUnref(pDbPage);
}
/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
DbPage *pDbPage; /* The pointer map page */
int iPtrmap; /* Pointer map page index */
u8 *pPtrmap; /* Pointer map page data */
int offset; /* Offset of entry in pointer map */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage, 0);
if( rc!=0 ){
return rc;
}
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
offset = PTRMAP_PTROFFSET(iPtrmap, key);
if( offset<0 ){
sqlite3PagerUnref(pDbPage);
return SQLITE_CORRUPT_BKPT;
}
assert( offset <= (int)pBt->usableSize-5 );
assert( pEType!=0 );
*pEType = pPtrmap[offset];
if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
sqlite3PagerUnref(pDbPage);
if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_PGNO(iPtrmap);
return SQLITE_OK;
}
#else /* if defined SQLITE_OMIT_AUTOVACUUM */
#define ptrmapPut(w,x,y,z,rc)
#define ptrmapGet(w,x,y,z) SQLITE_OK
#define ptrmapPutOvflPtr(x, y, z, rc)
#endif
/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** findCellPastPtr() does the same except it skips past the initial
** 4-byte child pointer found on interior pages, if there is one.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(P,I) \
((P)->aData + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
#define findCellPastPtr(P,I) \
((P)->aDataOfst + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
/*
** This is common tail processing for btreeParseCellPtr() and
** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
** on a single B-tree page. Make necessary adjustments to the CellInfo
** structure.
*/
static SQLITE_NOINLINE void btreeParseCellAdjustSizeForOverflow(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
/* If the payload will not fit completely on the local page, we have
** to decide how much to store locally and how much to spill onto
** overflow pages. The strategy is to minimize the amount of unused
** space on overflow pages while keeping the amount of local storage
** in between minLocal and maxLocal.
**
** Warning: changing the way overflow payload is distributed in any
** way will result in an incompatible file format.
*/
int minLocal; /* Minimum amount of payload held locally */
int maxLocal; /* Maximum amount of payload held locally */
int surplus; /* Overflow payload available for local storage */
minLocal = pPage->minLocal;
maxLocal = pPage->maxLocal;
surplus = minLocal + (pInfo->nPayload - minLocal)%(pPage->pBt->usableSize-4);
testcase( surplus==maxLocal );
testcase( surplus==maxLocal+1 );
if( surplus <= maxLocal ){
pInfo->nLocal = (u16)surplus;
}else{
pInfo->nLocal = (u16)minLocal;
}
pInfo->nSize = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell) + 4;
}
/*
** Given a record with nPayload bytes of payload stored within btree
** page pPage, return the number of bytes of payload stored locally.
*/
static int btreePayloadToLocal(MemPage *pPage, i64 nPayload){
int maxLocal; /* Maximum amount of payload held locally */
maxLocal = pPage->maxLocal;
if( nPayload<=maxLocal ){
return nPayload;
}else{
int minLocal; /* Minimum amount of payload held locally */
int surplus; /* Overflow payload available for local storage */
minLocal = pPage->minLocal;
surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize-4);
return ( surplus <= maxLocal ) ? surplus : minLocal;
}
}
/*
** The following routines are implementations of the MemPage.xParseCell()
** method.
**
** Parse a cell content block and fill in the CellInfo structure.
**
** btreeParseCellPtr() => table btree leaf nodes
** btreeParseCellNoPayload() => table btree internal nodes
** btreeParseCellPtrIndex() => index btree nodes
**
** There is also a wrapper function btreeParseCell() that works for
** all MemPage types and that references the cell by index rather than
** by pointer.
*/
static void btreeParseCellPtrNoPayload(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->leaf==0 );
assert( pPage->childPtrSize==4 );
#ifndef SQLITE_DEBUG
UNUSED_PARAMETER(pPage);
#endif
pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
pInfo->nPayload = 0;
pInfo->nLocal = 0;
pInfo->pPayload = 0;
return;
}
static void btreeParseCellPtr(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
u8 *pIter; /* For scanning through pCell */
u32 nPayload; /* Number of bytes of cell payload */
u64 iKey; /* Extracted Key value */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->leaf==0 || pPage->leaf==1 );
assert( pPage->intKeyLeaf );
assert( pPage->childPtrSize==0 );
pIter = pCell;
/* The next block of code is equivalent to:
**
** pIter += getVarint32(pIter, nPayload);
**
** The code is inlined to avoid a function call.
*/
nPayload = *pIter;
if( nPayload>=0x80 ){
u8 *pEnd = &pIter[8];
nPayload &= 0x7f;
do{
nPayload = (nPayload<<7) | (*++pIter & 0x7f);
}while( (*pIter)>=0x80 && pIter<pEnd );
}
pIter++;
/* The next block of code is equivalent to:
**
** pIter += getVarint(pIter, (u64*)&pInfo->nKey);
**
** The code is inlined to avoid a function call.
*/
iKey = *pIter;
if( iKey>=0x80 ){
u8 *pEnd = &pIter[7];
iKey &= 0x7f;
while(1){
iKey = (iKey<<7) | (*++pIter & 0x7f);
if( (*pIter)<0x80 ) break;
if( pIter>=pEnd ){
iKey = (iKey<<8) | *++pIter;
break;
}
}
}
pIter++;
pInfo->nKey = *(i64*)&iKey;
pInfo->nPayload = nPayload;
pInfo->pPayload = pIter;
testcase( nPayload==pPage->maxLocal );
testcase( nPayload==pPage->maxLocal+1 );
if( nPayload<=pPage->maxLocal ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
*/
pInfo->nSize = nPayload + (u16)(pIter - pCell);
if( pInfo->nSize<4 ) pInfo->nSize = 4;
pInfo->nLocal = (u16)nPayload;
}else{
btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
}
}
static void btreeParseCellPtrIndex(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
u8 *pIter; /* For scanning through pCell */
u32 nPayload; /* Number of bytes of cell payload */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->leaf==0 || pPage->leaf==1 );
assert( pPage->intKeyLeaf==0 );
pIter = pCell + pPage->childPtrSize;
nPayload = *pIter;
if( nPayload>=0x80 ){
u8 *pEnd = &pIter[8];
nPayload &= 0x7f;
do{
nPayload = (nPayload<<7) | (*++pIter & 0x7f);
}while( *(pIter)>=0x80 && pIter<pEnd );
}
pIter++;
pInfo->nKey = nPayload;
pInfo->nPayload = nPayload;
pInfo->pPayload = pIter;
testcase( nPayload==pPage->maxLocal );
testcase( nPayload==pPage->maxLocal+1 );
if( nPayload<=pPage->maxLocal ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
*/
pInfo->nSize = nPayload + (u16)(pIter - pCell);
if( pInfo->nSize<4 ) pInfo->nSize = 4;
pInfo->nLocal = (u16)nPayload;
}else{
btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
}
}
static void btreeParseCell(
MemPage *pPage, /* Page containing the cell */
int iCell, /* The cell index. First cell is 0 */
CellInfo *pInfo /* Fill in this structure */
){
pPage->xParseCell(pPage, findCell(pPage, iCell), pInfo);
}
/*
** The following routines are implementations of the MemPage.xCellSize
** method.
**
** Compute the total number of bytes that a Cell needs in the cell
** data area of the btree-page. The return number includes the cell
** data header and the local payload, but not any overflow page or
** the space used by the cell pointer.
**
** cellSizePtrNoPayload() => table internal nodes
** cellSizePtr() => all index nodes & table leaf nodes
*/
static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
u8 *pIter = pCell + pPage->childPtrSize; /* For looping over bytes of pCell */
u8 *pEnd; /* End mark for a varint */
u32 nSize; /* Size value to return */
#ifdef SQLITE_DEBUG
/* The value returned by this function should always be the same as
** the (CellInfo.nSize) value found by doing a full parse of the
** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
** this function verifies that this invariant is not violated. */
CellInfo debuginfo;
pPage->xParseCell(pPage, pCell, &debuginfo);
#endif
nSize = *pIter;
if( nSize>=0x80 ){
pEnd = &pIter[8];
nSize &= 0x7f;
do{
nSize = (nSize<<7) | (*++pIter & 0x7f);
}while( *(pIter)>=0x80 && pIter<pEnd );
}
pIter++;
if( pPage->intKey ){
/* pIter now points at the 64-bit integer key value, a variable length
** integer. The following block moves pIter to point at the first byte
** past the end of the key value. */
pEnd = &pIter[9];
while( (*pIter++)&0x80 && pIter<pEnd );
}
testcase( nSize==pPage->maxLocal );
testcase( nSize==pPage->maxLocal+1 );
if( nSize<=pPage->maxLocal ){
nSize += (u32)(pIter - pCell);
if( nSize<4 ) nSize = 4;
}else{
int minLocal = pPage->minLocal;
nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
testcase( nSize==pPage->maxLocal );
testcase( nSize==pPage->maxLocal+1 );
if( nSize>pPage->maxLocal ){
nSize = minLocal;
}
nSize += 4 + (u16)(pIter - pCell);
}
assert( nSize==debuginfo.nSize || CORRUPT_DB );
return (u16)nSize;
}
static u16 cellSizePtrNoPayload(MemPage *pPage, u8 *pCell){
u8 *pIter = pCell + 4; /* For looping over bytes of pCell */
u8 *pEnd; /* End mark for a varint */
#ifdef SQLITE_DEBUG
/* The value returned by this function should always be the same as
** the (CellInfo.nSize) value found by doing a full parse of the
** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
** this function verifies that this invariant is not violated. */
CellInfo debuginfo;
pPage->xParseCell(pPage, pCell, &debuginfo);
#else
UNUSED_PARAMETER(pPage);
#endif
assert( pPage->childPtrSize==4 );
pEnd = pIter + 9;
while( (*pIter++)&0x80 && pIter<pEnd );
assert( debuginfo.nSize==(u16)(pIter - pCell) || CORRUPT_DB );
return (u16)(pIter - pCell);
}
#ifdef SQLITE_DEBUG
/* This variation on cellSizePtr() is used inside of assert() statements
** only. */
static u16 cellSize(MemPage *pPage, int iCell){
return pPage->xCellSize(pPage, findCell(pPage, iCell));
}
#endif
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** The cell pCell is currently part of page pSrc but will ultimately be part
** of pPage. (pSrc and pPager are often the same.) If pCell contains a
** pointer to an overflow page, insert an entry into the pointer-map for
** the overflow page that will be valid after pCell has been moved to pPage.
*/
static void ptrmapPutOvflPtr(MemPage *pPage, MemPage *pSrc, u8 *pCell,int *pRC){
CellInfo info;
if( *pRC ) return;
assert( pCell!=0 );
pPage->xParseCell(pPage, pCell, &info);
if( info.nLocal<info.nPayload ){
Pgno ovfl;
if( SQLITE_WITHIN(pSrc->aDataEnd, pCell, pCell+info.nLocal) ){
testcase( pSrc!=pPage );
*pRC = SQLITE_CORRUPT_BKPT;
return;
}
ovfl = get4byte(&pCell[info.nSize-4]);
ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
}
}
#endif
/*
** Defragment the page given. This routine reorganizes cells within the
** page so that there are no free-blocks on the free-block list.
**
** Parameter nMaxFrag is the maximum amount of fragmented space that may be
** present in the page after this routine returns.
**
** EVIDENCE-OF: R-44582-60138 SQLite may from time to time reorganize a
** b-tree page so that there are no freeblocks or fragment bytes, all
** unused bytes are contained in the unallocated space region, and all
** cells are packed tightly at the end of the page.
*/
static int defragmentPage(MemPage *pPage, int nMaxFrag){
int i; /* Loop counter */
int pc; /* Address of the i-th cell */
int hdr; /* Offset to the page header */
int size; /* Size of a cell */
int usableSize; /* Number of usable bytes on a page */
int cellOffset; /* Offset to the cell pointer array */
int cbrk; /* Offset to the cell content area */
int nCell; /* Number of cells on the page */
unsigned char *data; /* The page data */
unsigned char *temp; /* Temp area for cell content */
unsigned char *src; /* Source of content */
int iCellFirst; /* First allowable cell index */
int iCellLast; /* Last possible cell index */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt!=0 );
assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
temp = 0;
src = data = pPage->aData;
hdr = pPage->hdrOffset;
cellOffset = pPage->cellOffset;
nCell = pPage->nCell;
assert( nCell==get2byte(&data[hdr+3]) || CORRUPT_DB );
iCellFirst = cellOffset + 2*nCell;
usableSize = pPage->pBt->usableSize;
/* This block handles pages with two or fewer free blocks and nMaxFrag
** or fewer fragmented bytes. In this case it is faster to move the
** two (or one) blocks of cells using memmove() and add the required
** offsets to each pointer in the cell-pointer array than it is to
** reconstruct the entire page. */
if( (int)data[hdr+7]<=nMaxFrag ){
int iFree = get2byte(&data[hdr+1]);
if( iFree>usableSize-4 ) return SQLITE_CORRUPT_PAGE(pPage);
if( iFree ){
int iFree2 = get2byte(&data[iFree]);
if( iFree2>usableSize-4 ) return SQLITE_CORRUPT_PAGE(pPage);
if( 0==iFree2 || (data[iFree2]==0 && data[iFree2+1]==0) ){
u8 *pEnd = &data[cellOffset + nCell*2];
u8 *pAddr;
int sz2 = 0;
int sz = get2byte(&data[iFree+2]);
int top = get2byte(&data[hdr+5]);
if( top>=iFree ){
return SQLITE_CORRUPT_PAGE(pPage);
}
if( iFree2 ){
if( iFree+sz>iFree2 ) return SQLITE_CORRUPT_PAGE(pPage);
sz2 = get2byte(&data[iFree2+2]);
if( iFree2+sz2 > usableSize ) return SQLITE_CORRUPT_PAGE(pPage);
memmove(&data[iFree+sz+sz2], &data[iFree+sz], iFree2-(iFree+sz));
sz += sz2;
}else if( NEVER(iFree+sz>usableSize) ){
return SQLITE_CORRUPT_PAGE(pPage);
}
cbrk = top+sz;
assert( cbrk+(iFree-top) <= usableSize );
memmove(&data[cbrk], &data[top], iFree-top);
for(pAddr=&data[cellOffset]; pAddr<pEnd; pAddr+=2){
pc = get2byte(pAddr);
if( pc<iFree ){ put2byte(pAddr, pc+sz); }
else if( pc<iFree2 ){ put2byte(pAddr, pc+sz2); }
}
goto defragment_out;
}
}
}
cbrk = usableSize;
iCellLast = usableSize - 4;
for(i=0; i<nCell; i++){
u8 *pAddr; /* The i-th cell pointer */
pAddr = &data[cellOffset + i*2];
pc = get2byte(pAddr);
testcase( pc==iCellFirst );
testcase( pc==iCellLast );
/* These conditions have already been verified in btreeInitPage()
** if PRAGMA cell_size_check=ON.
*/
if( pc<iCellFirst || pc>iCellLast ){
return SQLITE_CORRUPT_PAGE(pPage);
}
assert( pc>=iCellFirst && pc<=iCellLast );
size = pPage->xCellSize(pPage, &src[pc]);
cbrk -= size;
if( cbrk<iCellFirst || pc+size>usableSize ){
return SQLITE_CORRUPT_PAGE(pPage);
}
assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
testcase( cbrk+size==usableSize );
testcase( pc+size==usableSize );
put2byte(pAddr, cbrk);
if( temp==0 ){
int x;
if( cbrk==pc ) continue;
temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
x = get2byte(&data[hdr+5]);
memcpy(&temp[x], &data[x], (cbrk+size) - x);
src = temp;
}
memcpy(&data[cbrk], &src[pc], size);
}
data[hdr+7] = 0;
defragment_out:
assert( pPage->nFree>=0 );
if( data[hdr+7]+cbrk-iCellFirst!=pPage->nFree ){
return SQLITE_CORRUPT_PAGE(pPage);
}
assert( cbrk>=iCellFirst );
put2byte(&data[hdr+5], cbrk);
data[hdr+1] = 0;
data[hdr+2] = 0;
memset(&data[iCellFirst], 0, cbrk-iCellFirst);
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
return SQLITE_OK;
}
/*
** Search the free-list on page pPg for space to store a cell nByte bytes in
** size. If one can be found, return a pointer to the space and remove it
** from the free-list.
**
** If no suitable space can be found on the free-list, return NULL.
**
** This function may detect corruption within pPg. If corruption is
** detected then *pRc is set to SQLITE_CORRUPT and NULL is returned.
**
** Slots on the free list that are between 1 and 3 bytes larger than nByte
** will be ignored if adding the extra space to the fragmentation count
** causes the fragmentation count to exceed 60.
*/
static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
const int hdr = pPg->hdrOffset; /* Offset to page header */
u8 * const aData = pPg->aData; /* Page data */
int iAddr = hdr + 1; /* Address of ptr to pc */
int pc = get2byte(&aData[iAddr]); /* Address of a free slot */
int x; /* Excess size of the slot */
int maxPC = pPg->pBt->usableSize - nByte; /* Max address for a usable slot */
int size; /* Size of the free slot */
assert( pc>0 );
while( pc<=maxPC ){
/* EVIDENCE-OF: R-22710-53328 The third and fourth bytes of each
** freeblock form a big-endian integer which is the size of the freeblock
** in bytes, including the 4-byte header. */
size = get2byte(&aData[pc+2]);
if( (x = size - nByte)>=0 ){
testcase( x==4 );
testcase( x==3 );
if( x<4 ){
/* EVIDENCE-OF: R-11498-58022 In a well-formed b-tree page, the total
** number of bytes in fragments may not exceed 60. */
if( aData[hdr+7]>57 ) return 0;
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
memcpy(&aData[iAddr], &aData[pc], 2);
aData[hdr+7] += (u8)x;
}else if( x+pc > maxPC ){
/* This slot extends off the end of the usable part of the page */
*pRc = SQLITE_CORRUPT_PAGE(pPg);
return 0;
}else{
/* The slot remains on the free-list. Reduce its size to account
** for the portion used by the new allocation. */
put2byte(&aData[pc+2], x);
}
return &aData[pc + x];
}
iAddr = pc;
pc = get2byte(&aData[pc]);
if( pc<=iAddr+size ){
if( pc ){
/* The next slot in the chain is not past the end of the current slot */
*pRc = SQLITE_CORRUPT_PAGE(pPg);
}
return 0;
}
}
if( pc>maxPC+nByte-4 ){
/* The free slot chain extends off the end of the page */
*pRc = SQLITE_CORRUPT_PAGE(pPg);
}
return 0;
}
/*
** Allocate nByte bytes of space from within the B-Tree page passed
** as the first argument. Write into *pIdx the index into pPage->aData[]
** of the first byte of allocated space. Return either SQLITE_OK or
** an error code (usually SQLITE_CORRUPT).
**
** The caller guarantees that there is sufficient space to make the
** allocation. This routine might need to defragment in order to bring
** all the space together, however. This routine will avoid using
** the first two bytes past the cell pointer area since presumably this
** allocation is being made in order to insert a new cell, so we will
** also end up needing a new cell pointer.
*/
static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
const int hdr = pPage->hdrOffset; /* Local cache of pPage->hdrOffset */
u8 * const data = pPage->aData; /* Local cache of pPage->aData */
int top; /* First byte of cell content area */
int rc = SQLITE_OK; /* Integer return code */
int gap; /* First byte of gap between cell pointers and cell content */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( nByte>=0 ); /* Minimum cell size is 4 */
assert( pPage->nFree>=nByte );
assert( pPage->nOverflow==0 );
assert( nByte < (int)(pPage->pBt->usableSize-8) );
assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
gap = pPage->cellOffset + 2*pPage->nCell;
assert( gap<=65536 );
/* EVIDENCE-OF: R-29356-02391 If the database uses a 65536-byte page size
** and the reserved space is zero (the usual value for reserved space)
** then the cell content offset of an empty page wants to be 65536.
** However, that integer is too large to be stored in a 2-byte unsigned
** integer, so a value of 0 is used in its place. */
top = get2byte(&data[hdr+5]);
assert( top<=(int)pPage->pBt->usableSize ); /* by btreeComputeFreeSpace() */
if( gap>top ){
if( top==0 && pPage->pBt->usableSize==65536 ){
top = 65536;
}else{
return SQLITE_CORRUPT_PAGE(pPage);
}
}
/* If there is enough space between gap and top for one more cell pointer,
** and if the freelist is not empty, then search the
** freelist looking for a slot big enough to satisfy the request.
*/
testcase( gap+2==top );
testcase( gap+1==top );
testcase( gap==top );
if( (data[hdr+2] || data[hdr+1]) && gap+2<=top ){
u8 *pSpace = pageFindSlot(pPage, nByte, &rc);
if( pSpace ){
int g2;
assert( pSpace+nByte<=data+pPage->pBt->usableSize );
*pIdx = g2 = (int)(pSpace-data);
if( NEVER(g2<=gap) ){
return SQLITE_CORRUPT_PAGE(pPage);
}else{
return SQLITE_OK;
}
}else if( rc ){
return rc;
}
}
/* The request could not be fulfilled using a freelist slot. Check
** to see if defragmentation is necessary.
*/
testcase( gap+2+nByte==top );
if( gap+2+nByte>top ){
assert( pPage->nCell>0 || CORRUPT_DB );
assert( pPage->nFree>=0 );
rc = defragmentPage(pPage, MIN(4, pPage->nFree - (2+nByte)));
if( rc ) return rc;
top = get2byteNotZero(&data[hdr+5]);
assert( gap+2+nByte<=top );
}
/* Allocate memory from the gap in between the cell pointer array
** and the cell content area. The btreeComputeFreeSpace() call has already
** validated the freelist. Given that the freelist is valid, there
** is no way that the allocation can extend off the end of the page.
** The assert() below verifies the previous sentence.
*/
top -= nByte;
put2byte(&data[hdr+5], top);
assert( top+nByte <= (int)pPage->pBt->usableSize );
*pIdx = top;
return SQLITE_OK;
}
/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aData[iStart]
** and the size of the block is iSize bytes.
**
** Adjacent freeblocks are coalesced.
**
** Even though the freeblock list was checked by btreeComputeFreeSpace(),
** that routine will not detect overlap between cells or freeblocks. Nor
** does it detect cells or freeblocks that encrouch into the reserved bytes
** at the end of the page. So do additional corruption checks inside this
** routine and return SQLITE_CORRUPT if any problems are found.
*/
static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
u16 iPtr; /* Address of ptr to next freeblock */
u16 iFreeBlk; /* Address of the next freeblock */
u8 hdr; /* Page header size. 0 or 100 */
u8 nFrag = 0; /* Reduction in fragmentation */
u16 iOrigSize = iSize; /* Original value of iSize */
u16 x; /* Offset to cell content area */
u32 iEnd = iStart + iSize; /* First byte past the iStart buffer */
unsigned char *data = pPage->aData; /* Page content */
assert( pPage->pBt!=0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( CORRUPT_DB || iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
assert( CORRUPT_DB || iEnd <= pPage->pBt->usableSize );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( iSize>=4 ); /* Minimum cell size is 4 */
assert( iStart<=pPage->pBt->usableSize-4 );
/* The list of freeblocks must be in ascending order. Find the
** spot on the list where iStart should be inserted.
*/
hdr = pPage->hdrOffset;
iPtr = hdr + 1;
if( data[iPtr+1]==0 && data[iPtr]==0 ){
iFreeBlk = 0; /* Shortcut for the case when the freelist is empty */
}else{
while( (iFreeBlk = get2byte(&data[iPtr]))<iStart ){
if( iFreeBlk<iPtr+4 ){
if( iFreeBlk==0 ) break; /* TH3: corrupt082.100 */
return SQLITE_CORRUPT_PAGE(pPage);
}
iPtr = iFreeBlk;
}
if( iFreeBlk>pPage->pBt->usableSize-4 ){ /* TH3: corrupt081.100 */
return SQLITE_CORRUPT_PAGE(pPage);
}
assert( iFreeBlk>iPtr || iFreeBlk==0 );
/* At this point:
** iFreeBlk: First freeblock after iStart, or zero if none
** iPtr: The address of a pointer to iFreeBlk
**
** Check to see if iFreeBlk should be coalesced onto the end of iStart.
*/
if( iFreeBlk && iEnd+3>=iFreeBlk ){
nFrag = iFreeBlk - iEnd;
if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_PAGE(pPage);
iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
if( iEnd > pPage->pBt->usableSize ){
return SQLITE_CORRUPT_PAGE(pPage);
}
iSize = iEnd - iStart;
iFreeBlk = get2byte(&data[iFreeBlk]);
}
/* If iPtr is another freeblock (that is, if iPtr is not the freelist
** pointer in the page header) then check to see if iStart should be
** coalesced onto the end of iPtr.
*/
if( iPtr>hdr+1 ){
int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
if( iPtrEnd+3>=iStart ){
if( iPtrEnd>iStart ) return SQLITE_CORRUPT_PAGE(pPage);
nFrag += iStart - iPtrEnd;
iSize = iEnd - iPtr;
iStart = iPtr;
}
}
if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_PAGE(pPage);
data[hdr+7] -= nFrag;
}
x = get2byte(&data[hdr+5]);
if( iStart<=x ){
/* The new freeblock is at the beginning of the cell content area,
** so just extend the cell content area rather than create another
** freelist entry */
if( iStart<x ) return SQLITE_CORRUPT_PAGE(pPage);
if( iPtr!=hdr+1 ) return SQLITE_CORRUPT_PAGE(pPage);
put2byte(&data[hdr+1], iFreeBlk);
put2byte(&data[hdr+5], iEnd);
}else{
/* Insert the new freeblock into the freelist */
put2byte(&data[iPtr], iStart);
}
if( pPage->pBt->btsFlags & BTS_FAST_SECURE ){
/* Overwrite deleted information with zeros when the secure_delete
** option is enabled */
memset(&data[iStart], 0, iSize);
}
put2byte(&data[iStart], iFreeBlk);
put2byte(&data[iStart+2], iSize);
pPage->nFree += iOrigSize;
return SQLITE_OK;
}
/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**
** Only the following combinations are supported. Anything different
** indicates a corrupt database files:
**
** PTF_ZERODATA
** PTF_ZERODATA | PTF_LEAF
** PTF_LEAFDATA | PTF_INTKEY
** PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
*/
static int decodeFlags(MemPage *pPage, int flagByte){
BtShared *pBt; /* A copy of pPage->pBt */
assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->leaf = (u8)(flagByte>>3); assert( PTF_LEAF == 1<<3 );
flagByte &= ~PTF_LEAF;
pPage->childPtrSize = 4-4*pPage->leaf;
pPage->xCellSize = cellSizePtr;
pBt = pPage->pBt;
if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
/* EVIDENCE-OF: R-07291-35328 A value of 5 (0x05) means the page is an
** interior table b-tree page. */
assert( (PTF_LEAFDATA|PTF_INTKEY)==5 );
/* EVIDENCE-OF: R-26900-09176 A value of 13 (0x0d) means the page is a
** leaf table b-tree page. */
assert( (PTF_LEAFDATA|PTF_INTKEY|PTF_LEAF)==13 );
pPage->intKey = 1;
if( pPage->leaf ){
pPage->intKeyLeaf = 1;
pPage->xParseCell = btreeParseCellPtr;
}else{
pPage->intKeyLeaf = 0;
pPage->xCellSize = cellSizePtrNoPayload;
pPage->xParseCell = btreeParseCellPtrNoPayload;
}
pPage->maxLocal = pBt->maxLeaf;
pPage->minLocal = pBt->minLeaf;
}else if( flagByte==PTF_ZERODATA ){
/* EVIDENCE-OF: R-43316-37308 A value of 2 (0x02) means the page is an
** interior index b-tree page. */
assert( (PTF_ZERODATA)==2 );
/* EVIDENCE-OF: R-59615-42828 A value of 10 (0x0a) means the page is a
** leaf index b-tree page. */
assert( (PTF_ZERODATA|PTF_LEAF)==10 );
pPage->intKey = 0;
pPage->intKeyLeaf = 0;
pPage->xParseCell = btreeParseCellPtrIndex;
pPage->maxLocal = pBt->maxLocal;
pPage->minLocal = pBt->minLocal;
}else{
/* EVIDENCE-OF: R-47608-56469 Any other value for the b-tree page type is
** an error. */
return SQLITE_CORRUPT_PAGE(pPage);
}
pPage->max1bytePayload = pBt->max1bytePayload;
return SQLITE_OK;
}
/*
** Compute the amount of freespace on the page. In other words, fill
** in the pPage->nFree field.
*/
static int btreeComputeFreeSpace(MemPage *pPage){
int pc; /* Address of a freeblock within pPage->aData[] */
u8 hdr; /* Offset to beginning of page header */
u8 *data; /* Equal to pPage->aData */
int usableSize; /* Amount of usable space on each page */
int nFree; /* Number of unused bytes on the page */
int top; /* First byte of the cell content area */
int iCellFirst; /* First allowable cell or freeblock offset */
int iCellLast; /* Last possible cell or freeblock offset */
assert( pPage->pBt!=0 );
assert( pPage->pBt->db!=0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
assert( pPage->isInit==1 );
assert( pPage->nFree<0 );
usableSize = pPage->pBt->usableSize;
hdr = pPage->hdrOffset;
data = pPage->aData;
/* EVIDENCE-OF: R-58015-48175 The two-byte integer at offset 5 designates
** the start of the cell content area. A zero value for this integer is
** interpreted as 65536. */
top = get2byteNotZero(&data[hdr+5]);
iCellFirst = hdr + 8 + pPage->childPtrSize + 2*pPage->nCell;
iCellLast = usableSize - 4;
/* Compute the total free space on the page
** EVIDENCE-OF: R-23588-34450 The two-byte integer at offset 1 gives the
** start of the first freeblock on the page, or is zero if there are no
** freeblocks. */
pc = get2byte(&data[hdr+1]);
nFree = data[hdr+7] + top; /* Init nFree to non-freeblock free space */
if( pc>0 ){
u32 next, size;
if( pc<top ){
/* EVIDENCE-OF: R-55530-52930 In a well-formed b-tree page, there will
** always be at least one cell before the first freeblock.
*/
return SQLITE_CORRUPT_PAGE(pPage);
}
while( 1 ){
if( pc>iCellLast ){
/* Freeblock off the end of the page */
return SQLITE_CORRUPT_PAGE(pPage);
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
nFree = nFree + size;
if( next<=pc+size+3 ) break;
pc = next;
}
if( next>0 ){
/* Freeblock not in ascending order */
return SQLITE_CORRUPT_PAGE(pPage);
}
if( pc+size>(unsigned int)usableSize ){
/* Last freeblock extends past page end */
return SQLITE_CORRUPT_PAGE(pPage);
}
}
/* At this point, nFree contains the sum of the offset to the start
** of the cell-content area plus the number of free bytes within
** the cell-content area. If this is greater than the usable-size
** of the page, then the page must be corrupted. This check also
** serves to verify that the offset to the start of the cell-content
** area, according to the page header, lies within the page.
*/
if( nFree>usableSize || nFree<iCellFirst ){
return SQLITE_CORRUPT_PAGE(pPage);
}
pPage->nFree = (u16)(nFree - iCellFirst);
return SQLITE_OK;
}
/*
** Do additional sanity check after btreeInitPage() if
** PRAGMA cell_size_check=ON
*/
static SQLITE_NOINLINE int btreeCellSizeCheck(MemPage *pPage){
int iCellFirst; /* First allowable cell or freeblock offset */
int iCellLast; /* Last possible cell or freeblock offset */
int i; /* Index into the cell pointer array */
int sz; /* Size of a cell */
int pc; /* Address of a freeblock within pPage->aData[] */
u8 *data; /* Equal to pPage->aData */
int usableSize; /* Maximum usable space on the page */
int cellOffset; /* Start of cell content area */
iCellFirst = pPage->cellOffset + 2*pPage->nCell;
usableSize = pPage->pBt->usableSize;
iCellLast = usableSize - 4;
data = pPage->aData;
cellOffset = pPage->cellOffset;
if( !pPage->leaf ) iCellLast--;
for(i=0; i<pPage->nCell; i++){
pc = get2byteAligned(&data[cellOffset+i*2]);
testcase( pc==iCellFirst );
testcase( pc==iCellLast );
if( pc<iCellFirst || pc>iCellLast ){
return SQLITE_CORRUPT_PAGE(pPage);
}
sz = pPage->xCellSize(pPage, &data[pc]);
testcase( pc+sz==usableSize );
if( pc+sz>usableSize ){
return SQLITE_CORRUPT_PAGE(pPage);
}
}
return SQLITE_OK;
}
/*
** Initialize the auxiliary information for a disk block.
**
** Return SQLITE_OK on success. If we see that the page does
** not contain a well-formed database page, then return
** SQLITE_CORRUPT. Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed. It only shows that
** we failed to detect any corruption.
*/
static int btreeInitPage(MemPage *pPage){
u8 *data; /* Equal to pPage->aData */
BtShared *pBt; /* The main btree structure */
assert( pPage->pBt!=0 );
assert( pPage->pBt->db!=0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
assert( pPage->isInit==0 );
pBt = pPage->pBt;
data = pPage->aData + pPage->hdrOffset;
/* EVIDENCE-OF: R-28594-02890 The one-byte flag at offset 0 indicating
** the b-tree page type. */
if( decodeFlags(pPage, data[0]) ){
return SQLITE_CORRUPT_PAGE(pPage);
}
assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
pPage->maskPage = (u16)(pBt->pageSize - 1);
pPage->nOverflow = 0;
pPage->cellOffset = pPage->hdrOffset + 8 + pPage->childPtrSize;
pPage->aCellIdx = data + pPage->childPtrSize + 8;
pPage->aDataEnd = pPage->aData + pBt->usableSize;
pPage->aDataOfst = pPage->aData + pPage->childPtrSize;
/* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
** number of cells on the page. */
pPage->nCell = get2byte(&data[3]);
if( pPage->nCell>MX_CELL(pBt) ){
/* To many cells for a single page. The page must be corrupt */
return SQLITE_CORRUPT_PAGE(pPage);
}
testcase( pPage->nCell==MX_CELL(pBt) );
/* EVIDENCE-OF: R-24089-57979 If a page contains no cells (which is only
** possible for a root page of a table that contains no rows) then the
** offset to the cell content area will equal the page size minus the
** bytes of reserved space. */
assert( pPage->nCell>0
|| get2byteNotZero(&data[5])==(int)pBt->usableSize
|| CORRUPT_DB );
pPage->nFree = -1; /* Indicate that this value is yet uncomputed */
pPage->isInit = 1;
if( pBt->db->flags & SQLITE_CellSizeCk ){
return btreeCellSizeCheck(pPage);
}
return SQLITE_OK;
}
/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
unsigned char *data = pPage->aData;
BtShared *pBt = pPage->pBt;
u8 hdr = pPage->hdrOffset;
u16 first;
assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage) == data );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->btsFlags & BTS_FAST_SECURE ){
memset(&data[hdr], 0, pBt->usableSize - hdr);
}
data[hdr] = (char)flags;
first = hdr + ((flags&PTF_LEAF)==0 ? 12 : 8);
memset(&data[hdr+1], 0, 4);
data[hdr+7] = 0;
put2byte(&data[hdr+5], pBt->usableSize);
pPage->nFree = (u16)(pBt->usableSize - first);
decodeFlags(pPage, flags);
pPage->cellOffset = first;
pPage->aDataEnd = &data[pBt->usableSize];
pPage->aCellIdx = &data[first];
pPage->aDataOfst = &data[pPage->childPtrSize];
pPage->nOverflow = 0;
assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
pPage->maskPage = (u16)(pBt->pageSize - 1);
pPage->nCell = 0;
pPage->isInit = 1;
}
/*
** Convert a DbPage obtained from the pager into a MemPage used by
** the btree layer.
*/
static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
MemPage *pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
if( pgno!=pPage->pgno ){
pPage->aData = sqlite3PagerGetData(pDbPage);
pPage->pDbPage = pDbPage;
pPage->pBt = pBt;
pPage->pgno = pgno;
pPage->hdrOffset = pgno==1 ? 100 : 0;
}
assert( pPage->aData==sqlite3PagerGetData(pDbPage) );
return pPage;
}
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed. See also: btreeGetUnusedPage().
**
** If the PAGER_GET_NOCONTENT flag is set, it means that we do not care
** about the content of the page at this time. So do not go to the disk
** to fetch the content. Just fill in the content with zeros for now.
** If in the future we call sqlite3PagerWrite() on this page, that
** means we have started to be concerned about content and the disk
** read should occur at that point.
*/
static int btreeGetPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int flags /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
){
int rc;
DbPage *pDbPage;
assert( flags==0 || flags==PAGER_GET_NOCONTENT || flags==PAGER_GET_READONLY );
assert( sqlite3_mutex_held(pBt->mutex) );
rc = sqlite3PagerGet(pBt->pPager, pgno, (DbPage**)&pDbPage, flags);
if( rc ) return rc;
*ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
return SQLITE_OK;
}
/*
** Retrieve a page from the pager cache. If the requested page is not
** already in the pager cache return NULL. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
if( pDbPage ){
return btreePageFromDbPage(pDbPage, pgno, pBt);
}
return 0;
}
/*
** Return the size of the database file in pages. If there is any kind of
** error, return ((unsigned int)-1).
*/
static Pgno btreePagecount(BtShared *pBt){
return pBt->nPage;
}
Pgno sqlite3BtreeLastPage(Btree *p){
assert( sqlite3BtreeHoldsMutex(p) );
return btreePagecount(p->pBt);
}
/*
** Get a page from the pager and initialize it.
**
** If pCur!=0 then the page is being fetched as part of a moveToChild()
** call. Do additional sanity checking on the page in this case.
** And if the fetch fails, this routine must decrement pCur->iPage.
**
** The page is fetched as read-write unless pCur is not NULL and is
** a read-only cursor.
**
** If an error occurs, then *ppPage is undefined. It
** may remain unchanged, or it may be set to an invalid value.
*/
static int getAndInitPage(
BtShared *pBt, /* The database file */
Pgno pgno, /* Number of the page to get */
MemPage **ppPage, /* Write the page pointer here */
BtCursor *pCur, /* Cursor to receive the page, or NULL */
int bReadOnly /* True for a read-only page */
){
int rc;
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pCur==0 || ppPage==&pCur->pPage );
assert( pCur==0 || bReadOnly==pCur->curPagerFlags );
assert( pCur==0 || pCur->iPage>0 );
if( pgno>btreePagecount(pBt) ){
rc = SQLITE_CORRUPT_BKPT;
goto getAndInitPage_error1;
}
rc = sqlite3PagerGet(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadOnly);
if( rc ){
goto getAndInitPage_error1;
}
*ppPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
if( (*ppPage)->isInit==0 ){
btreePageFromDbPage(pDbPage, pgno, pBt);
rc = btreeInitPage(*ppPage);
if( rc!=SQLITE_OK ){
goto getAndInitPage_error2;
}
}
assert( (*ppPage)->pgno==pgno );
assert( (*ppPage)->aData==sqlite3PagerGetData(pDbPage) );
/* If obtaining a child page for a cursor, we must verify that the page is
** compatible with the root page. */
if( pCur && ((*ppPage)->nCell<1 || (*ppPage)->intKey!=pCur->curIntKey) ){
rc = SQLITE_CORRUPT_PGNO(pgno);
goto getAndInitPage_error2;
}
return SQLITE_OK;
getAndInitPage_error2:
releasePage(*ppPage);
getAndInitPage_error1:
if( pCur ){
pCur->iPage--;
pCur->pPage = pCur->apPage[pCur->iPage];
}
testcase( pgno==0 );
assert( pgno!=0 || rc==SQLITE_CORRUPT );
return rc;
}
/*
** Release a MemPage. This should be called once for each prior
** call to btreeGetPage.
**
** Page1 is a special case and must be released using releasePageOne().
*/
static void releasePageNotNull(MemPage *pPage){
assert( pPage->aData );
assert( pPage->pBt );
assert( pPage->pDbPage!=0 );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3PagerUnrefNotNull(pPage->pDbPage);
}
static void releasePage(MemPage *pPage){
if( pPage ) releasePageNotNull(pPage);
}
static void releasePageOne(MemPage *pPage){
assert( pPage!=0 );
assert( pPage->aData );
assert( pPage->pBt );
assert( pPage->pDbPage!=0 );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3PagerUnrefPageOne(pPage->pDbPage);
}
/*
** Get an unused page.
**
** This works just like btreeGetPage() with the addition:
**
** * If the page is already in use for some other purpose, immediately
** release it and return an SQLITE_CURRUPT error.
** * Make sure the isInit flag is clear
*/
static int btreeGetUnusedPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int flags /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
){
int rc = btreeGetPage(pBt, pgno, ppPage, flags);
if( rc==SQLITE_OK ){
if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
releasePage(*ppPage);
*ppPage = 0;
return SQLITE_CORRUPT_BKPT;
}
(*ppPage)->isInit = 0;
}else{
*ppPage = 0;
}
return rc;
}
/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
** This routine needs to reset the extra data section at the end of the
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData){
MemPage *pPage;
pPage = (MemPage *)sqlite3PagerGetExtra(pData);
assert( sqlite3PagerPageRefcount(pData)>0 );
if( pPage->isInit ){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->isInit = 0;
if( sqlite3PagerPageRefcount(pData)>1 ){
/* pPage might not be a btree page; it might be an overflow page
** or ptrmap page or a free page. In those cases, the following
** call to btreeInitPage() will likely return SQLITE_CORRUPT.
** But no harm is done by this. And it is very important that
** btreeInitPage() be called on every btree page so we make
** the call for every page that comes in for re-initing. */
btreeInitPage(pPage);
}
}
}
/*
** Invoke the busy handler for a btree.
*/
static int btreeInvokeBusyHandler(void *pArg){
BtShared *pBt = (BtShared*)pArg;
assert( pBt->db );
assert( sqlite3_mutex_held(pBt->db->mutex) );
return sqlite3InvokeBusyHandler(&pBt->db->busyHandler);
}
/*
** Open a database file.
**
** zFilename is the name of the database file. If zFilename is NULL
** then an ephemeral database is created. The ephemeral database might
** be exclusively in memory, or it might use a disk-based memory cache.
** Either way, the ephemeral database will be automatically deleted
** when sqlite3BtreeClose() is called.
**
** If zFilename is ":memory:" then an in-memory database is created
** that is automatically destroyed when it is closed.
**
** The "flags" parameter is a bitmask that might contain bits like
** BTREE_OMIT_JOURNAL and/or BTREE_MEMORY.
**
** If the database is already opened in the same database connection
** and we are in shared cache mode, then the open will fail with an
** SQLITE_CONSTRAINT error. We cannot allow two or more BtShared
** objects in the same database connection since doing so will lead
** to problems with locking.
*/
int sqlite3BtreeOpen(
sqlite3_vfs *pVfs, /* VFS to use for this b-tree */
const char *zFilename, /* Name of the file containing the BTree database */
sqlite3 *db, /* Associated database handle */
Btree **ppBtree, /* Pointer to new Btree object written here */
int flags, /* Options */
int vfsFlags /* Flags passed through to sqlite3_vfs.xOpen() */
){
BtShared *pBt = 0; /* Shared part of btree structure */
Btree *p; /* Handle to return */
sqlite3_mutex *mutexOpen = 0; /* Prevents a race condition. Ticket #3537 */
int rc = SQLITE_OK; /* Result code from this function */
u8 nReserve; /* Byte of unused space on each page */
unsigned char zDbHeader[100]; /* Database header content */
/* True if opening an ephemeral, temporary database */
const int isTempDb = zFilename==0 || zFilename[0]==0;
/* Set the variable isMemdb to true for an in-memory database, or
** false for a file-based database.
*/
#ifdef SQLITE_OMIT_MEMORYDB
const int isMemdb = 0;
#else
const int isMemdb = (zFilename && strcmp(zFilename, ":memory:")==0)
|| (isTempDb && sqlite3TempInMemory(db))
|| (vfsFlags & SQLITE_OPEN_MEMORY)!=0;
#endif
assert( db!=0 );
assert( pVfs!=0 );
assert( sqlite3_mutex_held(db->mutex) );
assert( (flags&0xff)==flags ); /* flags fit in 8 bits */
/* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
assert( (flags & BTREE_UNORDERED)==0 || (flags & BTREE_SINGLE)!=0 );
/* A BTREE_SINGLE database is always a temporary and/or ephemeral */
assert( (flags & BTREE_SINGLE)==0 || isTempDb );
if( isMemdb ){
flags |= BTREE_MEMORY;
}
if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (isMemdb || isTempDb) ){
vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
}
p = sqlite3MallocZero(sizeof(Btree));
if( !p ){
return SQLITE_NOMEM_BKPT;
}
p->inTrans = TRANS_NONE;
p->db = db;
#ifndef SQLITE_OMIT_SHARED_CACHE
p->lock.pBtree = p;
p->lock.iTable = 1;
#endif
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/*
** If this Btree is a candidate for shared cache, try to find an
** existing BtShared object that we can share with
*/
if( isTempDb==0 && (isMemdb==0 || (vfsFlags&SQLITE_OPEN_URI)!=0) ){
if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
int nFilename = sqlite3Strlen30(zFilename)+1;
int nFullPathname = pVfs->mxPathname+1;
char *zFullPathname = sqlite3Malloc(MAX(nFullPathname,nFilename));
MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
p->sharable = 1;
if( !zFullPathname ){
sqlite3_free(p);
return SQLITE_NOMEM_BKPT;
}
if( isMemdb ){
memcpy(zFullPathname, zFilename, nFilename);
}else{
rc = sqlite3OsFullPathname(pVfs, zFilename,
nFullPathname, zFullPathname);
if( rc ){
if( rc==SQLITE_OK_SYMLINK ){
rc = SQLITE_OK;
}else{
sqlite3_free(zFullPathname);
sqlite3_free(p);
return rc;
}
}
}
#if SQLITE_THREADSAFE
mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
sqlite3_mutex_enter(mutexOpen);
mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
sqlite3_mutex_enter(mutexShared);
#endif
for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
assert( pBt->nRef>0 );
if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager, 0))
&& sqlite3PagerVfs(pBt->pPager)==pVfs ){
int iDb;
for(iDb=db->nDb-1; iDb>=0; iDb--){
Btree *pExisting = db->aDb[iDb].pBt;
if( pExisting && pExisting->pBt==pBt ){
sqlite3_mutex_leave(mutexShared);
sqlite3_mutex_leave(mutexOpen);
sqlite3_free(zFullPathname);
sqlite3_free(p);
return SQLITE_CONSTRAINT;
}
}
p->pBt = pBt;
pBt->nRef++;
break;
}
}
sqlite3_mutex_leave(mutexShared);
sqlite3_free(zFullPathname);
}
#ifdef SQLITE_DEBUG
else{
/* In debug mode, we mark all persistent databases as sharable
** even when they are not. This exercises the locking code and
** gives more opportunity for asserts(sqlite3_mutex_held())
** statements to find locking problems.
*/
p->sharable = 1;
}
#endif
}
#endif
if( pBt==0 ){
/*
** The following asserts make sure that structures used by the btree are
** the right size. This is to guard against size changes that result
** when compiling on a different architecture.
*/
assert( sizeof(i64)==8 );
assert( sizeof(u64)==8 );
assert( sizeof(u32)==4 );
assert( sizeof(u16)==2 );
assert( sizeof(Pgno)==4 );
pBt = sqlite3MallocZero( sizeof(*pBt) );
if( pBt==0 ){
rc = SQLITE_NOMEM_BKPT;
goto btree_open_out;
}
rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
sizeof(MemPage), flags, vfsFlags, pageReinit);
if( rc==SQLITE_OK ){
sqlite3PagerSetMmapLimit(pBt->pPager, db->szMmap);
rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
}
if( rc!=SQLITE_OK ){
goto btree_open_out;
}
pBt->openFlags = (u8)flags;
pBt->db = db;
sqlite3PagerSetBusyHandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
p->pBt = pBt;
pBt->pCursor = 0;
pBt->pPage1 = 0;
if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
#if defined(SQLITE_SECURE_DELETE)
pBt->btsFlags |= BTS_SECURE_DELETE;
#elif defined(SQLITE_FAST_SECURE_DELETE)
pBt->btsFlags |= BTS_OVERWRITE;
#endif
/* EVIDENCE-OF: R-51873-39618 The page size for a database file is
** determined by the 2-byte integer located at an offset of 16 bytes from
** the beginning of the database file. */
pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
|| ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
pBt->pageSize = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the magic name ":memory:" will create an in-memory database, then
** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
** regular file-name. In this case the auto-vacuum applies as per normal.
*/
if( zFilename && !isMemdb ){
pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
}
#endif
nReserve = 0;
}else{
/* EVIDENCE-OF: R-37497-42412 The size of the reserved region is
** determined by the one-byte unsigned integer found at an offset of 20
** into the database file header. */
nReserve = zDbHeader[20];
pBt->btsFlags |= BTS_PAGESIZE_FIXED;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
#endif
}
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
if( rc ) goto btree_open_out;
pBt->usableSize = pBt->pageSize - nReserve;
assert( (pBt->pageSize & 7)==0 ); /* 8-byte alignment of pageSize */
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* Add the new BtShared object to the linked list sharable BtShareds.
*/
pBt->nRef = 1;
if( p->sharable ){
MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);)
if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
if( pBt->mutex==0 ){
rc = SQLITE_NOMEM_BKPT;
goto btree_open_out;
}
}
sqlite3_mutex_enter(mutexShared);
pBt->pNext = GLOBAL(BtShared*,sqlite3SharedCacheList);
GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt;
sqlite3_mutex_leave(mutexShared);
}
#endif
}
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* If the new Btree uses a sharable pBtShared, then link the new
** Btree into the list of all sharable Btrees for the same connection.
** The list is kept in ascending order by pBt address.
*/
if( p->sharable ){
int i;
Btree *pSib;
for(i=0; i<db->nDb; i++){
if( (pSib = db->aDb[i].pBt)!=0 && pSib->sharable ){
while( pSib->pPrev ){ pSib = pSib->pPrev; }
if( (uptr)p->pBt<(uptr)pSib->pBt ){
p->pNext = pSib;
p->pPrev = 0;
pSib->pPrev = p;
}else{
while( pSib->pNext && (uptr)pSib->pNext->pBt<(uptr)p->pBt ){
pSib = pSib->pNext;
}
p->pNext = pSib->pNext;
p->pPrev = pSib;
if( p->pNext ){
p->pNext->pPrev = p;
}
pSib->pNext = p;
}
break;
}
}
}
#endif
*ppBtree = p;
btree_open_out:
if( rc!=SQLITE_OK ){
if( pBt && pBt->pPager ){
sqlite3PagerClose(pBt->pPager, 0);
}
sqlite3_free(pBt);
sqlite3_free(p);
*ppBtree = 0;
}else{
sqlite3_file *pFile;
/* If the B-Tree was successfully opened, set the pager-cache size to the
** default value. Except, when opening on an existing shared pager-cache,
** do not change the pager-cache size.
*/
if( sqlite3BtreeSchema(p, 0, 0)==0 ){
sqlite3BtreeSetCacheSize(p, SQLITE_DEFAULT_CACHE_SIZE);
}
pFile = sqlite3PagerFile(pBt->pPager);
if( pFile->pMethods ){
sqlite3OsFileControlHint(pFile, SQLITE_FCNTL_PDB, (void*)&pBt->db);
}
}
if( mutexOpen ){
assert( sqlite3_mutex_held(mutexOpen) );
sqlite3_mutex_leave(mutexOpen);
}
assert( rc!=SQLITE_OK || sqlite3BtreeConnectionCount(*ppBtree)>0 );
return rc;
}
/*
** Decrement the BtShared.nRef counter. When it reaches zero,
** remove the BtShared structure from the sharing list. Return
** true if the BtShared.nRef counter reaches zero and return
** false if it is still positive.
*/
static int removeFromSharingList(BtShared *pBt){
#ifndef SQLITE_OMIT_SHARED_CACHE
MUTEX_LOGIC( sqlite3_mutex *pMainMtx; )
BtShared *pList;
int removed = 0;
assert( sqlite3_mutex_notheld(pBt->mutex) );
MUTEX_LOGIC( pMainMtx = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN); )
sqlite3_mutex_enter(pMainMtx);
pBt->nRef--;
if( pBt->nRef<=0 ){
if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;
}else{
pList = GLOBAL(BtShared*,sqlite3SharedCacheList);
while( ALWAYS(pList) && pList->pNext!=pBt ){
pList=pList->pNext;
}
if( ALWAYS(pList) ){
pList->pNext = pBt->pNext;
}
}
if( SQLITE_THREADSAFE ){
sqlite3_mutex_free(pBt->mutex);
}
removed = 1;
}
sqlite3_mutex_leave(pMainMtx);
return removed;
#else
return 1;
#endif
}
/*
** Make sure pBt->pTmpSpace points to an allocation of
** MX_CELL_SIZE(pBt) bytes with a 4-byte prefix for a left-child
** pointer.
*/
static void allocateTempSpace(BtShared *pBt){
if( !pBt->pTmpSpace ){
pBt->pTmpSpace = sqlite3PageMalloc( pBt->pageSize );
/* One of the uses of pBt->pTmpSpace is to format cells before
** inserting them into a leaf page (function fillInCell()). If
** a cell is less than 4 bytes in size, it is rounded up to 4 bytes
** by the various routines that manipulate binary cells. Which
** can mean that fillInCell() only initializes the first 2 or 3
** bytes of pTmpSpace, but that the first 4 bytes are copied from
** it into a database page. This is not actually a problem, but it
** does cause a valgrind error when the 1 or 2 bytes of unitialized
** data is passed to system call write(). So to avoid this error,
** zero the first 4 bytes of temp space here.
**
** Also: Provide four bytes of initialized space before the
** beginning of pTmpSpace as an area available to prepend the
** left-child pointer to the beginning of a cell.
*/
if( pBt->pTmpSpace ){
memset(pBt->pTmpSpace, 0, 8);
pBt->pTmpSpace += 4;
}
}
}
/*
** Free the pBt->pTmpSpace allocation
*/
static void freeTempSpace(BtShared *pBt){
if( pBt->pTmpSpace ){
pBt->pTmpSpace -= 4;
sqlite3PageFree(pBt->pTmpSpace);
pBt->pTmpSpace = 0;
}
}
/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *p){
BtShared *pBt = p->pBt;
/* Close all cursors opened via this handle. */
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
/* Verify that no other cursors have this Btree open */
#ifdef SQLITE_DEBUG
{
BtCursor *pCur = pBt->pCursor;
while( pCur ){
BtCursor *pTmp = pCur;
pCur = pCur->pNext;
assert( pTmp->pBtree!=p );
}
}
#endif
/* Rollback any active transaction and free the handle structure.
** The call to sqlite3BtreeRollback() drops any table-locks held by
** this handle.
*/
sqlite3BtreeRollback(p, SQLITE_OK, 0);
sqlite3BtreeLeave(p);
/* If there are still other outstanding references to the shared-btree
** structure, return now. The remainder of this procedure cleans
** up the shared-btree.
*/
assert( p->wantToLock==0 && p->locked==0 );
if( !p->sharable || removeFromSharingList(pBt) ){
/* The pBt is no longer on the sharing list, so we can access
** it without having to hold the mutex.
**
** Clean out and delete the BtShared object.
*/
assert( !pBt->pCursor );
sqlite3PagerClose(pBt->pPager, p->db);
if( pBt->xFreeSchema && pBt->pSchema ){
pBt->xFreeSchema(pBt->pSchema);
}
sqlite3DbFree(0, pBt->pSchema);
freeTempSpace(pBt);
sqlite3_free(pBt);
}
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( p->wantToLock==0 );
assert( p->locked==0 );
if( p->pPrev ) p->pPrev->pNext = p->pNext;
if( p->pNext ) p->pNext->pPrev = p->pPrev;
#endif
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Change the "soft" limit on the number of pages in the cache.
** Unused and unmodified pages will be recycled when the number of
** pages in the cache exceeds this soft limit. But the size of the
** cache is allowed to grow larger than this limit if it contains
** dirty pages or pages still in active use.
*/
int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetCachesize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Change the "spill" limit on the number of pages in the cache.
** If the number of pages exceeds this limit during a write transaction,
** the pager might attempt to "spill" pages to the journal early in
** order to free up memory.
**
** The value returned is the current spill size. If zero is passed
** as an argument, no changes are made to the spill size setting, so
** using mxPage of 0 is a way to query the current spill size.
*/
int sqlite3BtreeSetSpillSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
int res;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
res = sqlite3PagerSetSpillsize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return res;
}
#if SQLITE_MAX_MMAP_SIZE>0
/*
** Change the limit on the amount of the database file that may be
** memory mapped.
*/
int sqlite3BtreeSetMmapLimit(Btree *p, sqlite3_int64 szMmap){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetMmapLimit(pBt->pPager, szMmap);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
#endif /* SQLITE_MAX_MMAP_SIZE>0 */
/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures. Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage) Level 2 is the default. There
** is a very low but non-zero probability of damage. Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetPagerFlags(
Btree *p, /* The btree to set the safety level on */
unsigned pgFlags /* Various PAGER_* flags */
){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetFlags(pBt->pPager, pgFlags);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
#endif
/*
** Change the default pages size and the number of reserved bytes per page.
** Or, if the page size has already been fixed, return SQLITE_READONLY
** without changing anything.
**
** The page size must be a power of 2 between 512 and 65536. If the page
** size supplied does not meet this constraint then the page size is not
** changed.
**
** Page sizes are constrained to be a power of two so that the region
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
**
** If the iFix!=0 then the BTS_PAGESIZE_FIXED flag is set so that the page size
** and autovacuum mode can no longer be changed.
*/
int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
int rc = SQLITE_OK;
int x;
BtShared *pBt = p->pBt;
assert( nReserve>=0 && nReserve<=255 );
sqlite3BtreeEnter(p);
pBt->nReserveWanted = nReserve;
x = pBt->pageSize - pBt->usableSize;
if( nReserve<x ) nReserve = x;
if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
sqlite3BtreeLeave(p);
return SQLITE_READONLY;
}
assert( nReserve>=0 && nReserve<=255 );
if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
((pageSize-1)&pageSize)==0 ){
assert( (pageSize & 7)==0 );
assert( !pBt->pCursor );
if( nReserve>32 && pageSize==512 ) pageSize = 1024;
pBt->pageSize = (u32)pageSize;
freeTempSpace(pBt);
}
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
pBt->usableSize = pBt->pageSize - (u16)nReserve;
if( iFix ) pBt->btsFlags |= BTS_PAGESIZE_FIXED;
sqlite3BtreeLeave(p);
return rc;
}
/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
/*
** This function is similar to sqlite3BtreeGetReserve(), except that it
** may only be called if it is guaranteed that the b-tree mutex is already
** held.
**
** This is useful in one special case in the backup API code where it is
** known that the shared b-tree mutex is held, but the mutex on the
** database handle that owns *p is not. In this case if sqlite3BtreeEnter()
** were to be called, it might collide with some other operation on the
** database handle that owns *p, causing undefined behavior.
*/
int sqlite3BtreeGetReserveNoMutex(Btree *p){
int n;
assert( sqlite3_mutex_held(p->pBt->mutex) );
n = p->pBt->pageSize - p->pBt->usableSize;
return n;
}
/*
** Return the number of bytes of space at the end of every page that
** are intentually left unused. This is the "reserved" space that is
** sometimes used by extensions.
**
** The value returned is the larger of the current reserve size and
** the latest reserve size requested by SQLITE_FILECTRL_RESERVE_BYTES.
** The amount of reserve can only grow - never shrink.
*/
int sqlite3BtreeGetRequestedReserve(Btree *p){
int n1, n2;
sqlite3BtreeEnter(p);
n1 = (int)p->pBt->nReserveWanted;
n2 = sqlite3BtreeGetReserveNoMutex(p);
sqlite3BtreeLeave(p);
return n1>n2 ? n1 : n2;
}
/*
** Set the maximum page count for a database if mxPage is positive.
** No changes are made if mxPage is 0 or negative.
** Regardless of the value of mxPage, return the maximum page count.
*/
Pgno sqlite3BtreeMaxPageCount(Btree *p, Pgno mxPage){
Pgno n;
sqlite3BtreeEnter(p);
n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return n;
}
/*
** Change the values for the BTS_SECURE_DELETE and BTS_OVERWRITE flags:
**
** newFlag==0 Both BTS_SECURE_DELETE and BTS_OVERWRITE are cleared
** newFlag==1 BTS_SECURE_DELETE set and BTS_OVERWRITE is cleared
** newFlag==2 BTS_SECURE_DELETE cleared and BTS_OVERWRITE is set
** newFlag==(-1) No changes
**
** This routine acts as a query if newFlag is less than zero
**
** With BTS_OVERWRITE set, deleted content is overwritten by zeros, but
** freelist leaf pages are not written back to the database. Thus in-page
** deleted content is cleared, but freelist deleted content is not.
**
** With BTS_SECURE_DELETE, operation is like BTS_OVERWRITE with the addition
** that freelist leaf pages are written back into the database, increasing
** the amount of disk I/O.
*/
int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
int b;
if( p==0 ) return 0;
sqlite3BtreeEnter(p);
assert( BTS_OVERWRITE==BTS_SECURE_DELETE*2 );
assert( BTS_FAST_SECURE==(BTS_OVERWRITE|BTS_SECURE_DELETE) );
if( newFlag>=0 ){
p->pBt->btsFlags &= ~BTS_FAST_SECURE;
p->pBt->btsFlags |= BTS_SECURE_DELETE*newFlag;
}
b = (p->pBt->btsFlags & BTS_FAST_SECURE)/BTS_SECURE_DELETE;
sqlite3BtreeLeave(p);
return b;
}
/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
#ifdef SQLITE_OMIT_AUTOVACUUM
return SQLITE_READONLY;
#else
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
u8 av = (u8)autoVacuum;
sqlite3BtreeEnter(p);
if( (pBt->btsFlags & BTS_PAGESIZE_FIXED)!=0 && (av ?1:0)!=pBt->autoVacuum ){
rc = SQLITE_READONLY;
}else{
pBt->autoVacuum = av ?1:0;
pBt->incrVacuum = av==2 ?1:0;
}
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is
** enabled 1 is returned. Otherwise 0.
*/
int sqlite3BtreeGetAutoVacuum(Btree *p){
#ifdef SQLITE_OMIT_AUTOVACUUM
return BTREE_AUTOVACUUM_NONE;
#else
int rc;
sqlite3BtreeEnter(p);
rc = (
(!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
(!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
BTREE_AUTOVACUUM_INCR
);
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** If the user has not set the safety-level for this database connection
** using "PRAGMA synchronous", and if the safety-level is not already
** set to the value passed to this function as the second parameter,
** set it so.
*/
#if SQLITE_DEFAULT_SYNCHRONOUS!=SQLITE_DEFAULT_WAL_SYNCHRONOUS \
&& !defined(SQLITE_OMIT_WAL)
static void setDefaultSyncFlag(BtShared *pBt, u8 safety_level){
sqlite3 *db;
Db *pDb;
if( (db=pBt->db)!=0 && (pDb=db->aDb)!=0 ){
while( pDb->pBt==0 || pDb->pBt->pBt!=pBt ){ pDb++; }
if( pDb->bSyncSet==0
&& pDb->safety_level!=safety_level
&& pDb!=&db->aDb[1]
){
pDb->safety_level = safety_level;
sqlite3PagerSetFlags(pBt->pPager,
pDb->safety_level | (db->flags & PAGER_FLAGS_MASK));
}
}
}
#else
# define setDefaultSyncFlag(pBt,safety_level)
#endif
/* Forward declaration */
static int newDatabase(BtShared*);
/*
** Get a reference to pPage1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory.
*/
static int lockBtree(BtShared *pBt){
int rc; /* Result code from subfunctions */
MemPage *pPage1; /* Page 1 of the database file */
u32 nPage; /* Number of pages in the database */
u32 nPageFile = 0; /* Number of pages in the database file */
u32 nPageHeader; /* Number of pages in the database according to hdr */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pBt->pPage1==0 );
rc = sqlite3PagerSharedLock(pBt->pPager);
if( rc!=SQLITE_OK ) return rc;
rc = btreeGetPage(pBt, 1, &pPage1, 0);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
sqlite3PagerPagecount(pBt->pPager, (int*)&nPageFile);
if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
nPage = nPageFile;
}
if( (pBt->db->flags & SQLITE_ResetDatabase)!=0 ){
nPage = 0;
}
if( nPage>0 ){
u32 pageSize;
u32 usableSize;
u8 *page1 = pPage1->aData;
rc = SQLITE_NOTADB;
/* EVIDENCE-OF: R-43737-39999 Every valid SQLite database file begins
** with the following 16 bytes (in hex): 53 51 4c 69 74 65 20 66 6f 72 6d
** 61 74 20 33 00. */
if( memcmp(page1, zMagicHeader, 16)!=0 ){
goto page1_init_failed;
}
#ifdef SQLITE_OMIT_WAL
if( page1[18]>1 ){
pBt->btsFlags |= BTS_READ_ONLY;
}
if( page1[19]>1 ){
goto page1_init_failed;
}
#else
if( page1[18]>2 ){
pBt->btsFlags |= BTS_READ_ONLY;
}
if( page1[19]>2 ){
goto page1_init_failed;
}
/* If the write version is set to 2, this database should be accessed
** in WAL mode. If the log is not already open, open it now. Then
** return SQLITE_OK and return without populating BtShared.pPage1.
** The caller detects this and calls this function again. This is
** required as the version of page 1 currently in the page1 buffer
** may not be the latest version - there may be a newer one in the log
** file.
*/
if( page1[19]==2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
int isOpen = 0;
rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
if( rc!=SQLITE_OK ){
goto page1_init_failed;
}else{
setDefaultSyncFlag(pBt, SQLITE_DEFAULT_WAL_SYNCHRONOUS+1);
if( isOpen==0 ){
releasePageOne(pPage1);
return SQLITE_OK;
}
}
rc = SQLITE_NOTADB;
}else{
setDefaultSyncFlag(pBt, SQLITE_DEFAULT_SYNCHRONOUS+1);
}
#endif
/* EVIDENCE-OF: R-15465-20813 The maximum and minimum embedded payload
** fractions and the leaf payload fraction values must be 64, 32, and 32.
**
** The original design allowed these amounts to vary, but as of
** version 3.6.0, we require them to be fixed.
*/
if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
goto page1_init_failed;
}
/* EVIDENCE-OF: R-51873-39618 The page size for a database file is
** determined by the 2-byte integer located at an offset of 16 bytes from
** the beginning of the database file. */
pageSize = (page1[16]<<8) | (page1[17]<<16);
/* EVIDENCE-OF: R-25008-21688 The size of a page is a power of two
** between 512 and 65536 inclusive. */
if( ((pageSize-1)&pageSize)!=0
|| pageSize>SQLITE_MAX_PAGE_SIZE
|| pageSize<=256
){
goto page1_init_failed;
}
pBt->btsFlags |= BTS_PAGESIZE_FIXED;
assert( (pageSize & 7)==0 );
/* EVIDENCE-OF: R-59310-51205 The "reserved space" size in the 1-byte
** integer at offset 20 is the number of bytes of space at the end of
** each page to reserve for extensions.
**
** EVIDENCE-OF: R-37497-42412 The size of the reserved region is
** determined by the one-byte unsigned integer found at an offset of 20
** into the database file header. */
usableSize = pageSize - page1[20];
if( (u32)pageSize!=pBt->pageSize ){
/* After reading the first page of the database assuming a page size
** of BtShared.pageSize, we have discovered that the page-size is
** actually pageSize. Unlock the database, leave pBt->pPage1 at
** zero and return SQLITE_OK. The caller will call this function
** again with the correct page-size.
*/
releasePageOne(pPage1);
pBt->usableSize = usableSize;
pBt->pageSize = pageSize;
freeTempSpace(pBt);
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize,
pageSize-usableSize);
return rc;
}
if( sqlite3WritableSchema(pBt->db)==0 && nPage>nPageFile ){
rc = SQLITE_CORRUPT_BKPT;
goto page1_init_failed;
}
/* EVIDENCE-OF: R-28312-64704 However, the usable size is not allowed to
** be less than 480. In other words, if the page size is 512, then the
** reserved space size cannot exceed 32. */
if( usableSize<480 ){
goto page1_init_failed;
}
pBt->pageSize = pageSize;
pBt->usableSize = usableSize;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
#endif
}
/* maxLocal is the maximum amount of payload to store locally for
** a cell. Make sure it is small enough so that at least minFanout
** cells can will fit on one page. We assume a 10-byte page header.
** Besides the payload, the cell must store:
** 2-byte pointer to the cell
** 4-byte child pointer
** 9-byte nKey value
** 4-byte nData value
** 4-byte overflow page pointer
** So a cell consists of a 2-byte pointer, a header which is as much as
** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
** page pointer.
*/
pBt->maxLocal = (u16)((pBt->usableSize-12)*64/255 - 23);
pBt->minLocal = (u16)((pBt->usableSize-12)*32/255 - 23);
pBt->maxLeaf = (u16)(pBt->usableSize - 35);
pBt->minLeaf = (u16)((pBt->usableSize-12)*32/255 - 23);
if( pBt->maxLocal>127 ){
pBt->max1bytePayload = 127;
}else{
pBt->max1bytePayload = (u8)pBt->maxLocal;
}
assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
pBt->pPage1 = pPage1;
pBt->nPage = nPage;
return SQLITE_OK;
page1_init_failed:
releasePageOne(pPage1);
pBt->pPage1 = 0;
return rc;
}
#ifndef NDEBUG
/*
** Return the number of cursors open on pBt. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** Only write cursors are counted if wrOnly is true. If wrOnly is
** false then all cursors are counted.
**
** For the purposes of this routine, a cursor is any cursor that
** is capable of reading or writing to the database. Cursors that
** have been tripped into the CURSOR_FAULT state are not counted.
*/
static int countValidCursors(BtShared *pBt, int wrOnly){
BtCursor *pCur;
int r = 0;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( (wrOnly==0 || (pCur->curFlags & BTCF_WriteFlag)!=0)
&& pCur->eState!=CURSOR_FAULT ) r++;
}
return r;
}
#endif
/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which
** has the effect of releasing the read lock.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
assert( sqlite3_mutex_held(pBt->mutex) );
assert( countValidCursors(pBt,0)==0 || pBt->inTransaction>TRANS_NONE );
if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
MemPage *pPage1 = pBt->pPage1;
assert( pPage1->aData );
assert( sqlite3PagerRefcount(pBt->pPager)==1 );
pBt->pPage1 = 0;
releasePageOne(pPage1);
}
}
/*
** If pBt points to an empty file then convert that empty file
** into a new empty database by initializing the first page of
** the database.
*/
static int newDatabase(BtShared *pBt){
MemPage *pP1;
unsigned char *data;
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->nPage>0 ){
return SQLITE_OK;
}
pP1 = pBt->pPage1;
assert( pP1!=0 );
data = pP1->aData;
rc = sqlite3PagerWrite(pP1->pDbPage);
if( rc ) return rc;
memcpy(data, zMagicHeader, sizeof(zMagicHeader));
assert( sizeof(zMagicHeader)==16 );
data[16] = (u8)((pBt->pageSize>>8)&0xff);
data[17] = (u8)((pBt->pageSize>>16)&0xff);
data[18] = 1;
data[19] = 1;
assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);
data[20] = (u8)(pBt->pageSize - pBt->usableSize);
data[21] = 64;
data[22] = 32;
data[23] = 32;
memset(&data[24], 0, 100-24);
zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
pBt->btsFlags |= BTS_PAGESIZE_FIXED;
#ifndef SQLITE_OMIT_AUTOVACUUM
assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
put4byte(&data[36 + 4*4], pBt->autoVacuum);
put4byte(&data[36 + 7*4], pBt->incrVacuum);
#endif
pBt->nPage = 1;
data[31] = 1;
return SQLITE_OK;
}
/*
** Initialize the first page of the database file (creating a database
** consisting of a single page and no schema objects). Return SQLITE_OK
** if successful, or an SQLite error code otherwise.
*/
int sqlite3BtreeNewDb(Btree *p){
int rc;
sqlite3BtreeEnter(p);
p->pBt->nPage = 0;
rc = newDatabase(p->pBt);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Attempt to start a new transaction. A write-transaction
** is started if the second argument is nonzero, otherwise a read-
** transaction. If the second argument is 2 or more and exclusive
** transaction is started, meaning that no other process is allowed
** to access the database. A preexisting transaction may not be
** upgraded to exclusive by calling this routine a second time - the
** exclusivity flag only works for a new transaction.
**
** A write-transaction must be started before attempting any
** changes to the database. None of the following routines
** will work unless a transaction is started first:
**
** sqlite3BtreeCreateTable()
** sqlite3BtreeCreateIndex()
** sqlite3BtreeClearTable()
** sqlite3BtreeDropTable()
** sqlite3BtreeInsert()
** sqlite3BtreeDelete()
** sqlite3BtreeUpdateMeta()
**
** If an initial attempt to acquire the lock fails because of lock contention
** and the database was previously unlocked, then invoke the busy handler
** if there is one. But if there was previously a read-lock, do not
** invoke the busy handler - just return SQLITE_BUSY. SQLITE_BUSY is
** returned when there is already a read-lock in order to avoid a deadlock.
**
** Suppose there are two processes A and B. A has a read lock and B has
** a reserved lock. B tries to promote to exclusive but is blocked because
** of A's read lock. A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress. By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *p, int wrflag, int *pSchemaVersion){
BtShared *pBt = p->pBt;
Pager *pPager = pBt->pPager;
int rc = SQLITE_OK;
sqlite3BtreeEnter(p);
btreeIntegrity(p);
/* If the btree is already in a write-transaction, or it
** is already in a read-transaction and a read-transaction
** is requested, this is a no-op.
*/
if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
goto trans_begun;
}
assert( pBt->inTransaction==TRANS_WRITE || IfNotOmitAV(pBt->bDoTruncate)==0 );
if( (p->db->flags & SQLITE_ResetDatabase)
&& sqlite3PagerIsreadonly(pPager)==0
){
pBt->btsFlags &= ~BTS_READ_ONLY;
}
/* Write transactions are not possible on a read-only database */
if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
rc = SQLITE_READONLY;
goto trans_begun;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
{
sqlite3 *pBlock = 0;
/* If another database handle has already opened a write transaction
** on this shared-btree structure and a second write transaction is
** requested, return SQLITE_LOCKED.
*/
if( (wrflag && pBt->inTransaction==TRANS_WRITE)
|| (pBt->btsFlags & BTS_PENDING)!=0
){
pBlock = pBt->pWriter->db;
}else if( wrflag>1 ){
BtLock *pIter;
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p ){
pBlock = pIter->pBtree->db;
break;
}
}
}
if( pBlock ){
sqlite3ConnectionBlocked(p->db, pBlock);
rc = SQLITE_LOCKED_SHAREDCACHE;
goto trans_begun;
}
}
#endif
/* Any read-only or read-write transaction implies a read-lock on
** page 1. So if some other shared-cache client already has a write-lock
** on page 1, the transaction cannot be opened. */
rc = querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK);
if( SQLITE_OK!=rc ) goto trans_begun;
pBt->btsFlags &= ~BTS_INITIALLY_EMPTY;
if( pBt->nPage==0 ) pBt->btsFlags |= BTS_INITIALLY_EMPTY;
do {
sqlite3PagerWalDb(pPager, p->db);
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
/* If transitioning from no transaction directly to a write transaction,
** block for the WRITER lock first if possible. */
if( pBt->pPage1==0 && wrflag ){
assert( pBt->inTransaction==TRANS_NONE );
rc = sqlite3PagerWalWriteLock(pPager, 1);
if( rc!=SQLITE_BUSY && rc!=SQLITE_OK ) break;
}
#endif
/* Call lockBtree() until either pBt->pPage1 is populated or
** lockBtree() returns something other than SQLITE_OK. lockBtree()
** may return SQLITE_OK but leave pBt->pPage1 set to 0 if after
** reading page 1 it discovers that the page-size of the database
** file is not pBt->pageSize. In this case lockBtree() will update
** pBt->pageSize to the page-size of the file on disk.
*/
while( pBt->pPage1==0 && SQLITE_OK==(rc = lockBtree(pBt)) );
if( rc==SQLITE_OK && wrflag ){
if( (pBt->btsFlags & BTS_READ_ONLY)!=0 ){
rc = SQLITE_READONLY;
}else{
rc = sqlite3PagerBegin(pPager, wrflag>1, sqlite3TempInMemory(p->db));
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}else if( rc==SQLITE_BUSY_SNAPSHOT && pBt->inTransaction==TRANS_NONE ){
/* if there was no transaction opened when this function was
** called and SQLITE_BUSY_SNAPSHOT is returned, change the error
** code to SQLITE_BUSY. */
rc = SQLITE_BUSY;
}
}
}
if( rc!=SQLITE_OK ){
(void)sqlite3PagerWalWriteLock(pPager, 0);
unlockBtreeIfUnused(pBt);
}
}while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
btreeInvokeBusyHandler(pBt) );
sqlite3PagerWalDb(pPager, 0);
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
if( rc==SQLITE_BUSY_TIMEOUT ) rc = SQLITE_BUSY;
#endif
if( rc==SQLITE_OK ){
if( p->inTrans==TRANS_NONE ){
pBt->nTransaction++;
#ifndef SQLITE_OMIT_SHARED_CACHE
if( p->sharable ){
assert( p->lock.pBtree==p && p->lock.iTable==1 );
p->lock.eLock = READ_LOCK;
p->lock.pNext = pBt->pLock;
pBt->pLock = &p->lock;
}
#endif
}
p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
if( p->inTrans>pBt->inTransaction ){
pBt->inTransaction = p->inTrans;
}
if( wrflag ){
MemPage *pPage1 = pBt->pPage1;
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( !pBt->pWriter );
pBt->pWriter = p;
pBt->btsFlags &= ~BTS_EXCLUSIVE;
if( wrflag>1 ) pBt->btsFlags |= BTS_EXCLUSIVE;
#endif
/* If the db-size header field is incorrect (as it may be if an old
** client has been writing the database file), update it now. Doing
** this sooner rather than later means the database size can safely
** re-read the database size from page 1 if a savepoint or transaction
** rollback occurs within the transaction.
*/
if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pPage1->aData[28], pBt->nPage);
}
}
}
}
trans_begun:
if( rc==SQLITE_OK ){
if( pSchemaVersion ){
*pSchemaVersion = get4byte(&pBt->pPage1->aData[40]);
}
if( wrflag ){
/* This call makes sure that the pager has the correct number of
** open savepoints. If the second parameter is greater than 0 and
** the sub-journal is not already open, then it will be opened here.
*/
rc = sqlite3PagerOpenSavepoint(pPager, p->db->nSavepoint);
}
}
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Set the pointer-map entries for all children of page pPage. Also, if
** pPage contains cells that point to overflow pages, set the pointer
** map entries for the overflow pages as well.
*/
static int setChildPtrmaps(MemPage *pPage){
int i; /* Counter variable */
int nCell; /* Number of cells in page pPage */
int rc; /* Return code */
BtShared *pBt = pPage->pBt;
Pgno pgno = pPage->pgno;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
rc = pPage->isInit ? SQLITE_OK : btreeInitPage(pPage);
if( rc!=SQLITE_OK ) return rc;
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
ptrmapPutOvflPtr(pPage, pPage, pCell, &rc);
if( !pPage->leaf ){
Pgno childPgno = get4byte(pCell);
ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
}
}
if( !pPage->leaf ){
Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
}
return rc;
}
/*
** Somewhere on pPage is a pointer to page iFrom. Modify this pointer so
** that it points to iTo. Parameter eType describes the type of pointer to
** be modified, as follows:
**
** PTRMAP_BTREE: pPage is a btree-page. The pointer points at a child
** page of pPage.
**
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
** page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
** overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
if( eType==PTRMAP_OVERFLOW2 ){
/* The pointer is always the first 4 bytes of the page in this case. */
if( get4byte(pPage->aData)!=iFrom ){
return SQLITE_CORRUPT_PAGE(pPage);
}
put4byte(pPage->aData, iTo);
}else{
int i;
int nCell;
int rc;
rc = pPage->isInit ? SQLITE_OK : btreeInitPage(pPage);
if( rc ) return rc;
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
if( eType==PTRMAP_OVERFLOW1 ){
CellInfo info;
pPage->xParseCell(pPage, pCell, &info);
if( info.nLocal<info.nPayload ){
if( pCell+info.nSize > pPage->aData+pPage->pBt->usableSize ){
return SQLITE_CORRUPT_PAGE(pPage);
}
if( iFrom==get4byte(pCell+info.nSize-4) ){
put4byte(pCell+info.nSize-4, iTo);
break;
}
}
}else{
if( get4byte(pCell)==iFrom ){
put4byte(pCell, iTo);
break;
}
}
}
if( i==nCell ){
if( eType!=PTRMAP_BTREE ||
get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
return SQLITE_CORRUPT_PAGE(pPage);
}
put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
}
}
return SQLITE_OK;
}
/*
** Move the open database page pDbPage to location iFreePage in the
** database. The pDbPage reference remains valid.
**
** The isCommit flag indicates that there is no need to remember that
** the journal needs to be sync()ed before database page pDbPage->pgno
** can be written to. The caller has already promised not to write to that
** page.
*/
static int relocatePage(
BtShared *pBt, /* Btree */
MemPage *pDbPage, /* Open page to move */
u8 eType, /* Pointer map 'type' entry for pDbPage */
Pgno iPtrPage, /* Pointer map 'page-no' entry for pDbPage */
Pgno iFreePage, /* The location to move pDbPage to */
int isCommit /* isCommit flag passed to sqlite3PagerMovepage */
){
MemPage *pPtrPage; /* The page that contains a pointer to pDbPage */
Pgno iDbPage = pDbPage->pgno;
Pager *pPager = pBt->pPager;
int rc;
assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 ||
eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pDbPage->pBt==pBt );
if( iDbPage<3 ) return SQLITE_CORRUPT_BKPT;
/* Move page iDbPage from its current location to page number iFreePage */
TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n",
iDbPage, iFreePage, iPtrPage, eType));
rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
if( rc!=SQLITE_OK ){
return rc;
}
pDbPage->pgno = iFreePage;
/* If pDbPage was a btree-page, then it may have child pages and/or cells
** that point to overflow pages. The pointer map entries for all these
** pages need to be changed.
**
** If pDbPage is an overflow page, then the first 4 bytes may store a
** pointer to a subsequent overflow page. If this is the case, then
** the pointer map needs to be updated for the subsequent overflow page.
*/
if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
rc = setChildPtrmaps(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
Pgno nextOvfl = get4byte(pDbPage->aData);
if( nextOvfl!=0 ){
ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage, &rc);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
/* Fix the database pointer on page iPtrPage that pointed at iDbPage so
** that it points at iFreePage. Also fix the pointer map entry for
** iPtrPage.
*/
if( eType!=PTRMAP_ROOTPAGE ){
rc = btreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pPtrPage->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pPtrPage);
return rc;
}
rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
releasePage(pPtrPage);
if( rc==SQLITE_OK ){
ptrmapPut(pBt, iFreePage, eType, iPtrPage, &rc);
}
}
return rc;
}
/* Forward declaration required by incrVacuumStep(). */
static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
/*
** Perform a single step of an incremental-vacuum. If successful, return
** SQLITE_OK. If there is no work to do (and therefore no point in
** calling this function again), return SQLITE_DONE. Or, if an error
** occurs, return some other error code.
**
** More specifically, this function attempts to re-organize the database so
** that the last page of the file currently in use is no longer in use.
**
** Parameter nFin is the number of pages that this database would contain
** were this function called until it returns SQLITE_DONE.
**
** If the bCommit parameter is non-zero, this function assumes that the
** caller will keep calling incrVacuumStep() until it returns SQLITE_DONE
** or an error. bCommit is passed true for an auto-vacuum-on-commit
** operation, or false for an incremental vacuum.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
Pgno nFreeList; /* Number of pages still on the free-list */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( iLastPg>nFin );
if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
u8 eType;
Pgno iPtrPage;
nFreeList = get4byte(&pBt->pPage1->aData[36]);
if( nFreeList==0 ){
return SQLITE_DONE;
}
rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_ROOTPAGE ){
return SQLITE_CORRUPT_BKPT;
}
if( eType==PTRMAP_FREEPAGE ){
if( bCommit==0 ){
/* Remove the page from the files free-list. This is not required
** if bCommit is non-zero. In that case, the free-list will be
** truncated to zero after this function returns, so it doesn't
** matter if it still contains some garbage entries.
*/
Pgno iFreePg;
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, BTALLOC_EXACT);
if( rc!=SQLITE_OK ){
return rc;
}
assert( iFreePg==iLastPg );
releasePage(pFreePg);
}
} else {
Pgno iFreePg; /* Index of free page to move pLastPg to */
MemPage *pLastPg;
u8 eMode = BTALLOC_ANY; /* Mode parameter for allocateBtreePage() */
Pgno iNear = 0; /* nearby parameter for allocateBtreePage() */
rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
/* If bCommit is zero, this loop runs exactly once and page pLastPg
** is swapped with the first free page pulled off the free list.
**
** On the other hand, if bCommit is greater than zero, then keep
** looping until a free-page located within the first nFin pages
** of the file is found.
*/
if( bCommit==0 ){
eMode = BTALLOC_LE;
iNear = nFin;
}
do {
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iNear, eMode);
if( rc!=SQLITE_OK ){
releasePage(pLastPg);
return rc;
}
releasePage(pFreePg);
}while( bCommit && iFreePg>nFin );
assert( iFreePg<iLastPg );
rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, bCommit);
releasePage(pLastPg);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
if( bCommit==0 ){
do {
iLastPg--;
}while( iLastPg==PENDING_BYTE_PAGE(pBt) || PTRMAP_ISPAGE(pBt, iLastPg) );
pBt->bDoTruncate = 1;
pBt->nPage = iLastPg;
}
return SQLITE_OK;
}
/*
** The database opened by the first argument is an auto-vacuum database
** nOrig pages in size containing nFree free pages. Return the expected
** size of the database in pages following an auto-vacuum operation.
*/
static Pgno finalDbSize(BtShared *pBt, Pgno nOrig, Pgno nFree){
int nEntry; /* Number of entries on one ptrmap page */
Pgno nPtrmap; /* Number of PtrMap pages to be freed */
Pgno nFin; /* Return value */
nEntry = pBt->usableSize/5;
nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
nFin = nOrig - nFree - nPtrmap;
if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
return nFin;
}
/*
** A write-transaction must be opened before calling this function.
** It performs a single unit of work towards an incremental vacuum.
**
** If the incremental vacuum is finished after this function has run,
** SQLITE_DONE is returned. If it is not finished, but no error occurred,
** SQLITE_OK is returned. Otherwise an SQLite error code.
*/
int sqlite3BtreeIncrVacuum(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
if( !pBt->autoVacuum ){
rc = SQLITE_DONE;
}else{
Pgno nOrig = btreePagecount(pBt);
Pgno nFree = get4byte(&pBt->pPage1->aData[36]);
Pgno nFin = finalDbSize(pBt, nOrig, nFree);
if( nOrig<nFin || nFree>=nOrig ){
rc = SQLITE_CORRUPT_BKPT;
}else if( nFree>0 ){
rc = saveAllCursors(pBt, 0, 0);
if( rc==SQLITE_OK ){
invalidateAllOverflowCache(pBt);
rc = incrVacuumStep(pBt, nFin, nOrig, 0);
}
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
put4byte(&pBt->pPage1->aData[28], pBt->nPage);
}
}else{
rc = SQLITE_DONE;
}
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** This routine is called prior to sqlite3PagerCommit when a transaction
** is committed for an auto-vacuum database.
**
** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
** the database file should be truncated to during the commit process.
** i.e. the database has been reorganized so that only the first *pnTrunc
** pages are in use.
*/
static int autoVacuumCommit(BtShared *pBt){
int rc = SQLITE_OK;
Pager *pPager = pBt->pPager;
VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager); )
assert( sqlite3_mutex_held(pBt->mutex) );
invalidateAllOverflowCache(pBt);
assert(pBt->autoVacuum);
if( !pBt->incrVacuum ){
Pgno nFin; /* Number of pages in database after autovacuuming */
Pgno nFree; /* Number of pages on the freelist initially */
Pgno iFree; /* The next page to be freed */
Pgno nOrig; /* Database size before freeing */
nOrig = btreePagecount(pBt);
if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
/* It is not possible to create a database for which the final page
** is either a pointer-map page or the pending-byte page. If one
** is encountered, this indicates corruption.
*/
return SQLITE_CORRUPT_BKPT;
}
nFree = get4byte(&pBt->pPage1->aData[36]);
nFin = finalDbSize(pBt, nOrig, nFree);
if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
if( nFin<nOrig ){
rc = saveAllCursors(pBt, 0, 0);
}
for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
rc = incrVacuumStep(pBt, nFin, iFree, 1);
}
if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
put4byte(&pBt->pPage1->aData[32], 0);
put4byte(&pBt->pPage1->aData[36], 0);
put4byte(&pBt->pPage1->aData[28], nFin);
pBt->bDoTruncate = 1;
pBt->nPage = nFin;
}
if( rc!=SQLITE_OK ){
sqlite3PagerRollback(pPager);
}
}
assert( nRef>=sqlite3PagerRefcount(pPager) );
return rc;
}
#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
# define setChildPtrmaps(x) SQLITE_OK
#endif
/*
** This routine does the first phase of a two-phase commit. This routine
** causes a rollback journal to be created (if it does not already exist)
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal. Then the contents of the journal are flushed out to
** the disk. After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed. See sqlite3BtreeCommitPhaseTwo() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zSuperJrnl points to
** the name of a super-journal file that should be written into the
** individual journal file, or is NULL, indicating no super-journal file
** (single database transaction).
**
** When this is called, the super-journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zSuperJrnl){
int rc = SQLITE_OK;
if( p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
rc = autoVacuumCommit(pBt);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
}
if( pBt->bDoTruncate ){
sqlite3PagerTruncateImage(pBt->pPager, pBt->nPage);
}
#endif
rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zSuperJrnl, 0);
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
** at the conclusion of a transaction.
*/
static void btreeEndTransaction(Btree *p){
BtShared *pBt = p->pBt;
sqlite3 *db = p->db;
assert( sqlite3BtreeHoldsMutex(p) );
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->bDoTruncate = 0;
#endif
if( p->inTrans>TRANS_NONE && db->nVdbeRead>1 ){
/* If there are other active statements that belong to this database
** handle, downgrade to a read-only transaction. The other statements
** may still be reading from the database. */
downgradeAllSharedCacheTableLocks(p);
p->inTrans = TRANS_READ;
}else{
/* If the handle had any kind of transaction open, decrement the
** transaction count of the shared btree. If the transaction count
** reaches 0, set the shared state to TRANS_NONE. The unlockBtreeIfUnused()
** call below will unlock the pager. */
if( p->inTrans!=TRANS_NONE ){
clearAllSharedCacheTableLocks(p);
pBt->nTransaction--;
if( 0==pBt->nTransaction ){
pBt->inTransaction = TRANS_NONE;
}
}
/* Set the current transaction state to TRANS_NONE and unlock the
** pager if this call closed the only read or write transaction. */
p->inTrans = TRANS_NONE;
unlockBtreeIfUnused(pBt);
}
btreeIntegrity(p);
}
/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit. The
** sqlite3BtreeCommitPhaseOne() routine does the first phase and should
** be invoked prior to calling this routine. The sqlite3BtreeCommitPhaseOne()
** routine did all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter. All this
** routine has to do is delete or truncate or zero the header in the
** the rollback journal (which causes the transaction to commit) and
** drop locks.
**
** Normally, if an error occurs while the pager layer is attempting to
** finalize the underlying journal file, this function returns an error and
** the upper layer will attempt a rollback. However, if the second argument
** is non-zero then this b-tree transaction is part of a multi-file
** transaction. In this case, the transaction has already been committed
** (by deleting a super-journal file) and the caller will ignore this
** functions return code. So, even if an error occurs in the pager layer,
** reset the b-tree objects internal state to indicate that the write
** transaction has been closed. This is quite safe, as the pager will have
** transitioned to the error state.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommitPhaseTwo(Btree *p, int bCleanup){
if( p->inTrans==TRANS_NONE ) return SQLITE_OK;
sqlite3BtreeEnter(p);
btreeIntegrity(p);
/* If the handle has a write-transaction open, commit the shared-btrees
** transaction and set the shared state to TRANS_READ.
*/
if( p->inTrans==TRANS_WRITE ){
int rc;
BtShared *pBt = p->pBt;
assert( pBt->inTransaction==TRANS_WRITE );
assert( pBt->nTransaction>0 );
rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
if( rc!=SQLITE_OK && bCleanup==0 ){
sqlite3BtreeLeave(p);
return rc;
}
p->iBDataVersion--; /* Compensate for pPager->iDataVersion++; */
pBt->inTransaction = TRANS_READ;
btreeClearHasContent(pBt);
}
btreeEndTransaction(p);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Do both phases of a commit.
*/
int sqlite3BtreeCommit(Btree *p){
int rc;
sqlite3BtreeEnter(p);
rc = sqlite3BtreeCommitPhaseOne(p, 0);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeCommitPhaseTwo(p, 0);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on any BtShared that pBtree
** references. Or if the writeOnly flag is set to 1, then only
** trip write cursors and leave read cursors unchanged.
**
** Every cursor is a candidate to be tripped, including cursors
** that belong to other database connections that happen to be
** sharing the cache with pBtree.
**
** This routine gets called when a rollback occurs. If the writeOnly
** flag is true, then only write-cursors need be tripped - read-only
** cursors save their current positions so that they may continue
** following the rollback. Or, if writeOnly is false, all cursors are
** tripped. In general, writeOnly is false if the transaction being
** rolled back modified the database schema. In this case b-tree root
** pages may be moved or deleted from the database altogether, making
** it unsafe for read cursors to continue.
**
** If the writeOnly flag is true and an error is encountered while
** saving the current position of a read-only cursor, all cursors,
** including all read-cursors are tripped.
**
** SQLITE_OK is returned if successful, or if an error occurs while
** saving a cursor position, an SQLite error code.
*/
int sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode, int writeOnly){
BtCursor *p;
int rc = SQLITE_OK;
assert( (writeOnly==0 || writeOnly==1) && BTCF_WriteFlag==1 );
if( pBtree ){
sqlite3BtreeEnter(pBtree);
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
if( writeOnly && (p->curFlags & BTCF_WriteFlag)==0 ){
if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
rc = saveCursorPosition(p);
if( rc!=SQLITE_OK ){
(void)sqlite3BtreeTripAllCursors(pBtree, rc, 0);
break;
}
}
}else{
sqlite3BtreeClearCursor(p);
p->eState = CURSOR_FAULT;
p->skipNext = errCode;
}
btreeReleaseAllCursorPages(p);
}
sqlite3BtreeLeave(pBtree);
}
return rc;
}
/*
** Set the pBt->nPage field correctly, according to the current
** state of the database. Assume pBt->pPage1 is valid.
*/
static void btreeSetNPage(BtShared *pBt, MemPage *pPage1){
int nPage = get4byte(&pPage1->aData[28]);
testcase( nPage==0 );
if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
testcase( pBt->nPage!=nPage );
pBt->nPage = nPage;
}
/*
** Rollback the transaction in progress.
**
** If tripCode is not SQLITE_OK then cursors will be invalidated (tripped).
** Only write cursors are tripped if writeOnly is true but all cursors are
** tripped if writeOnly is false. Any attempt to use
** a tripped cursor will result in an error.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeRollback(Btree *p, int tripCode, int writeOnly){
int rc;
BtShared *pBt = p->pBt;
MemPage *pPage1;
assert( writeOnly==1 || writeOnly==0 );
assert( tripCode==SQLITE_ABORT_ROLLBACK || tripCode==SQLITE_OK );
sqlite3BtreeEnter(p);
if( tripCode==SQLITE_OK ){
rc = tripCode = saveAllCursors(pBt, 0, 0);
if( rc ) writeOnly = 0;
}else{
rc = SQLITE_OK;
}
if( tripCode ){
int rc2 = sqlite3BtreeTripAllCursors(p, tripCode, writeOnly);
assert( rc==SQLITE_OK || (writeOnly==0 && rc2==SQLITE_OK) );
if( rc2!=SQLITE_OK ) rc = rc2;
}
btreeIntegrity(p);
if( p->inTrans==TRANS_WRITE ){
int rc2;
assert( TRANS_WRITE==pBt->inTransaction );
rc2 = sqlite3PagerRollback(pBt->pPager);
if( rc2!=SQLITE_OK ){
rc = rc2;
}
/* The rollback may have destroyed the pPage1->aData value. So
** call btreeGetPage() on page 1 again to make
** sure pPage1->aData is set correctly. */
if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
btreeSetNPage(pBt, pPage1);
releasePageOne(pPage1);
}
assert( countValidCursors(pBt, 1)==0 );
pBt->inTransaction = TRANS_READ;
btreeClearHasContent(pBt);
}
btreeEndTransaction(p);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Start a statement subtransaction. The subtransaction can be rolled
** back independently of the main transaction. You must start a transaction
** before starting a subtransaction. The subtransaction is ended automatically
** if the main transaction commits or rolls back.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block. If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
**
** A statement sub-transaction is implemented as an anonymous savepoint. The
** value passed as the second parameter is the total number of savepoints,
** including the new anonymous savepoint, open on the B-Tree. i.e. if there
** are no active savepoints and no other statement-transactions open,
** iStatement is 1. This anonymous savepoint can be released or rolled back
** using the sqlite3BtreeSavepoint() function.
*/
int sqlite3BtreeBeginStmt(Btree *p, int iStatement){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( p->inTrans==TRANS_WRITE );
assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
assert( iStatement>0 );
assert( iStatement>p->db->nSavepoint );
assert( pBt->inTransaction==TRANS_WRITE );
/* At the pager level, a statement transaction is a savepoint with
** an index greater than all savepoints created explicitly using
** SQL statements. It is illegal to open, release or rollback any
** such savepoints while the statement transaction savepoint is active.
*/
rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
sqlite3BtreeLeave(p);
return rc;
}
/*
** The second argument to this function, op, is always SAVEPOINT_ROLLBACK
** or SAVEPOINT_RELEASE. This function either releases or rolls back the
** savepoint identified by parameter iSavepoint, depending on the value
** of op.
**
** Normally, iSavepoint is greater than or equal to zero. However, if op is
** SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the
** contents of the entire transaction are rolled back. This is different
** from a normal transaction rollback, as no locks are released and the
** transaction remains open.
*/
int sqlite3BtreeSavepoint(Btree *p, int op, int iSavepoint){
int rc = SQLITE_OK;
if( p && p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
sqlite3BtreeEnter(p);
if( op==SAVEPOINT_ROLLBACK ){
rc = saveAllCursors(pBt, 0, 0);
}
if( rc==SQLITE_OK ){
rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
}
if( rc==SQLITE_OK ){
if( iSavepoint<0 && (pBt->btsFlags & BTS_INITIALLY_EMPTY)!=0 ){
pBt->nPage = 0;
}
rc = newDatabase(pBt);
btreeSetNPage(pBt, pBt->pPage1);
/* pBt->nPage might be zero if the database was corrupt when
** the transaction was started. Otherwise, it must be at least 1. */
assert( CORRUPT_DB || pBt->nPage>0 );
}
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** Create a new cursor for the BTree whose root is on the page
** iTable. If a read-only cursor is requested, it is assumed that
** the caller already has at least a read-only transaction open
** on the database already. If a write-cursor is requested, then
** the caller is assumed to have an open write transaction.
**
** If the BTREE_WRCSR bit of wrFlag is clear, then the cursor can only
** be used for reading. If the BTREE_WRCSR bit is set, then the cursor
** can be used for reading or for writing if other conditions for writing
** are also met. These are the conditions that must be met in order
** for writing to be allowed:
**
** 1: The cursor must have been opened with wrFlag containing BTREE_WRCSR
**
** 2: Other database connections that share the same pager cache
** but which are not in the READ_UNCOMMITTED state may not have
** cursors open with wrFlag==0 on the same table. Otherwise
** the changes made by this write cursor would be visible to
** the read cursors in the other database connection.
**
** 3: The database must be writable (not on read-only media)
**
** 4: There must be an active transaction.
**
** The BTREE_FORDELETE bit of wrFlag may optionally be set if BTREE_WRCSR
** is set. If FORDELETE is set, that is a hint to the implementation that
** this cursor will only be used to seek to and delete entries of an index
** as part of a larger DELETE statement. The FORDELETE hint is not used by
** this implementation. But in a hypothetical alternative storage engine
** in which index entries are automatically deleted when corresponding table
** rows are deleted, the FORDELETE flag is a hint that all SEEK and DELETE
** operations on this cursor can be no-ops and all READ operations can
** return a null row (2-bytes: 0x01 0x00).
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree. If it is not, then the cursor acquired
** will not work correctly.
**
** It is assumed that the sqlite3BtreeCursorZero() has been called
** on pCur to initialize the memory space prior to invoking this routine.
*/
static int btreeCursor(
Btree *p, /* The btree */
Pgno iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to comparison function */
BtCursor *pCur /* Space for new cursor */
){
BtShared *pBt = p->pBt; /* Shared b-tree handle */
BtCursor *pX; /* Looping over other all cursors */
assert( sqlite3BtreeHoldsMutex(p) );
assert( wrFlag==0
|| wrFlag==BTREE_WRCSR
|| wrFlag==(BTREE_WRCSR|BTREE_FORDELETE)
);
/* The following assert statements verify that if this is a sharable
** b-tree database, the connection is holding the required table locks,
** and that no other connection has any open cursor that conflicts with
** this lock. The iTable<1 term disables the check for corrupt schemas. */
assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, (wrFlag?2:1))
|| iTable<1 );
assert( wrFlag==0 || !hasReadConflicts(p, iTable) );
/* Assert that the caller has opened the required transaction. */
assert( p->inTrans>TRANS_NONE );
assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
assert( pBt->pPage1 && pBt->pPage1->aData );
assert( wrFlag==0 || (pBt->btsFlags & BTS_READ_ONLY)==0 );
if( wrFlag ){
allocateTempSpace(pBt);
if( pBt->pTmpSpace==0 ) return SQLITE_NOMEM_BKPT;
}
if( iTable<=1 ){
if( iTable<1 ){
return SQLITE_CORRUPT_BKPT;
}else if( btreePagecount(pBt)==0 ){
assert( wrFlag==0 );
iTable = 0;
}
}
/* Now that no other errors can occur, finish filling in the BtCursor
** variables and link the cursor into the BtShared list. */
pCur->pgnoRoot = iTable;
pCur->iPage = -1;
pCur->pKeyInfo = pKeyInfo;
pCur->pBtree = p;
pCur->pBt = pBt;
pCur->curFlags = wrFlag ? BTCF_WriteFlag : 0;
pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY;
/* If there are two or more cursors on the same btree, then all such
** cursors *must* have the BTCF_Multiple flag set. */
for(pX=pBt->pCursor; pX; pX=pX->pNext){
if( pX->pgnoRoot==iTable ){
pX->curFlags |= BTCF_Multiple;
pCur->curFlags |= BTCF_Multiple;
}
}
pCur->pNext = pBt->pCursor;
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}
static int btreeCursorWithLock(
Btree *p, /* The btree */
Pgno iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to comparison function */
BtCursor *pCur /* Space for new cursor */
){
int rc;
sqlite3BtreeEnter(p);
rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
sqlite3BtreeLeave(p);
return rc;
}
int sqlite3BtreeCursor(
Btree *p, /* The btree */
Pgno iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to xCompare() */
BtCursor *pCur /* Write new cursor here */
){
if( p->sharable ){
return btreeCursorWithLock(p, iTable, wrFlag, pKeyInfo, pCur);
}else{
return btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
}
}
/*
** Return the size of a BtCursor object in bytes.
**
** This interfaces is needed so that users of cursors can preallocate
** sufficient storage to hold a cursor. The BtCursor object is opaque
** to users so they cannot do the sizeof() themselves - they must call
** this routine.
*/
int sqlite3BtreeCursorSize(void){
return ROUND8(sizeof(BtCursor));
}
/*
** Initialize memory that will be converted into a BtCursor object.
**
** The simple approach here would be to memset() the entire object
** to zero. But it turns out that the apPage[] and aiIdx[] arrays
** do not need to be zeroed and they are large, so we can save a lot
** of run-time by skipping the initialization of those elements.
*/
void sqlite3BtreeCursorZero(BtCursor *p){
memset(p, 0, offsetof(BtCursor, BTCURSOR_FIRST_UNINIT));
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
Btree *pBtree = pCur->pBtree;
if( pBtree ){
BtShared *pBt = pCur->pBt;
sqlite3BtreeEnter(pBtree);
assert( pBt->pCursor!=0 );
if( pBt->pCursor==pCur ){
pBt->pCursor = pCur->pNext;
}else{
BtCursor *pPrev = pBt->pCursor;
do{
if( pPrev->pNext==pCur ){
pPrev->pNext = pCur->pNext;
break;
}
pPrev = pPrev->pNext;
}while( ALWAYS(pPrev) );
}
btreeReleaseAllCursorPages(pCur);
unlockBtreeIfUnused(pBt);
sqlite3_free(pCur->aOverflow);
sqlite3_free(pCur->pKey);
if( (pBt->openFlags & BTREE_SINGLE) && pBt->pCursor==0 ){
/* Since the BtShared is not sharable, there is no need to
** worry about the missing sqlite3BtreeLeave() call here. */
assert( pBtree->sharable==0 );
sqlite3BtreeClose(pBtree);
}else{
sqlite3BtreeLeave(pBtree);
}
pCur->pBtree = 0;
}
return SQLITE_OK;
}
/*
** Make sure the BtCursor* given in the argument has a valid
** BtCursor.info structure. If it is not already valid, call
** btreeParseCell() to fill it in.
**
** BtCursor.info is a cache of the information in the current cell.
** Using this cache reduces the number of calls to btreeParseCell().
*/
#ifndef NDEBUG
static int cellInfoEqual(CellInfo *a, CellInfo *b){
if( a->nKey!=b->nKey ) return 0;
if( a->pPayload!=b->pPayload ) return 0;
if( a->nPayload!=b->nPayload ) return 0;
if( a->nLocal!=b->nLocal ) return 0;
if( a->nSize!=b->nSize ) return 0;
return 1;
}
static void assertCellInfo(BtCursor *pCur){
CellInfo info;
memset(&info, 0, sizeof(info));
btreeParseCell(pCur->pPage, pCur->ix, &info);
assert( CORRUPT_DB || cellInfoEqual(&info, &pCur->info) );
}
#else
#define assertCellInfo(x)
#endif
static SQLITE_NOINLINE void getCellInfo(BtCursor *pCur){
if( pCur->info.nSize==0 ){
pCur->curFlags |= BTCF_ValidNKey;
btreeParseCell(pCur->pPage,pCur->ix,&pCur->info);
}else{
assertCellInfo(pCur);
}
}
#ifndef NDEBUG /* The next routine used only within assert() statements */
/*
** Return true if the given BtCursor is valid. A valid cursor is one
** that is currently pointing to a row in a (non-empty) table.
** This is a verification routine is used only within assert() statements.
*/
int sqlite3BtreeCursorIsValid(BtCursor *pCur){
return pCur && pCur->eState==CURSOR_VALID;
}
#endif /* NDEBUG */
int sqlite3BtreeCursorIsValidNN(BtCursor *pCur){
assert( pCur!=0 );
return pCur->eState==CURSOR_VALID;
}
/*
** Return the value of the integer key or "rowid" for a table btree.
** This routine is only valid for a cursor that is pointing into a
** ordinary table btree. If the cursor points to an index btree or
** is invalid, the result of this routine is undefined.
*/
i64 sqlite3BtreeIntegerKey(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->curIntKey );
getCellInfo(pCur);
return pCur->info.nKey;
}
/*
** Pin or unpin a cursor.
*/
void sqlite3BtreeCursorPin(BtCursor *pCur){
assert( (pCur->curFlags & BTCF_Pinned)==0 );
pCur->curFlags |= BTCF_Pinned;
}
void sqlite3BtreeCursorUnpin(BtCursor *pCur){
assert( (pCur->curFlags & BTCF_Pinned)!=0 );
pCur->curFlags &= ~BTCF_Pinned;
}
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
/*
** Return the offset into the database file for the start of the
** payload to which the cursor is pointing.
*/
i64 sqlite3BtreeOffset(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
getCellInfo(pCur);
return (i64)pCur->pBt->pageSize*((i64)pCur->pPage->pgno - 1) +
(i64)(pCur->info.pPayload - pCur->pPage->aData);
}
#endif /* SQLITE_ENABLE_OFFSET_SQL_FUNC */
/*
** Return the number of bytes of payload for the entry that pCur is
** currently pointing to. For table btrees, this will be the amount
** of data. For index btrees, this will be the size of the key.
**
** The caller must guarantee that the cursor is pointing to a non-NULL
** valid entry. In other words, the calling procedure must guarantee
** that the cursor has Cursor.eState==CURSOR_VALID.
*/
u32 sqlite3BtreePayloadSize(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
getCellInfo(pCur);
return pCur->info.nPayload;
}
/*
** Return an upper bound on the size of any record for the table
** that the cursor is pointing into.
**
** This is an optimization. Everything will still work if this
** routine always returns 2147483647 (which is the largest record
** that SQLite can handle) or more. But returning a smaller value might
** prevent large memory allocations when trying to interpret a
** corrupt datrabase.
**
** The current implementation merely returns the size of the underlying
** database file.
*/
sqlite3_int64 sqlite3BtreeMaxRecordSize(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
return pCur->pBt->pageSize * (sqlite3_int64)pCur->pBt->nPage;
}
/*
** Given the page number of an overflow page in the database (parameter
** ovfl), this function finds the page number of the next page in the
** linked list of overflow pages. If possible, it uses the auto-vacuum
** pointer-map data instead of reading the content of page ovfl to do so.
**
** If an error occurs an SQLite error code is returned. Otherwise:
**
** The page number of the next overflow page in the linked list is
** written to *pPgnoNext. If page ovfl is the last page in its linked
** list, *pPgnoNext is set to zero.
**
** If ppPage is not NULL, and a reference to the MemPage object corresponding
** to page number pOvfl was obtained, then *ppPage is set to point to that
** reference. It is the responsibility of the caller to call releasePage()
** on *ppPage to free the reference. In no reference was obtained (because
** the pointer-map was used to obtain the value for *pPgnoNext), then
** *ppPage is set to zero.
*/
static int getOverflowPage(
BtShared *pBt, /* The database file */
Pgno ovfl, /* Current overflow page number */
MemPage **ppPage, /* OUT: MemPage handle (may be NULL) */
Pgno *pPgnoNext /* OUT: Next overflow page number */
){
Pgno next = 0;
MemPage *pPage = 0;
int rc = SQLITE_OK;
assert( sqlite3_mutex_held(pBt->mutex) );
assert(pPgnoNext);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* Try to find the next page in the overflow list using the
** autovacuum pointer-map pages. Guess that the next page in
** the overflow list is page number (ovfl+1). If that guess turns
** out to be wrong, fall back to loading the data of page
** number ovfl to determine the next page number.
*/
if( pBt->autoVacuum ){
Pgno pgno;
Pgno iGuess = ovfl+1;
u8 eType;
while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
iGuess++;
}
if( iGuess<=btreePagecount(pBt) ){
rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
next = iGuess;
rc = SQLITE_DONE;
}
}
}
#endif
assert( next==0 || rc==SQLITE_DONE );
if( rc==SQLITE_OK ){
rc = btreeGetPage(pBt, ovfl, &pPage, (ppPage==0) ? PAGER_GET_READONLY : 0);
assert( rc==SQLITE_OK || pPage==0 );
if( rc==SQLITE_OK ){
next = get4byte(pPage->aData);
}
}
*pPgnoNext = next;
if( ppPage ){
*ppPage = pPage;
}else{
releasePage(pPage);
}
return (rc==SQLITE_DONE ? SQLITE_OK : rc);
}
/*
** Copy data from a buffer to a page, or from a page to a buffer.
**
** pPayload is a pointer to data stored on database page pDbPage.
** If argument eOp is false, then nByte bytes of data are copied
** from pPayload to the buffer pointed at by pBuf. If eOp is true,
** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
** of data are copied from the buffer pBuf to pPayload.
**
** SQLITE_OK is returned on success, otherwise an error code.
*/
static int copyPayload(
void *pPayload, /* Pointer to page data */
void *pBuf, /* Pointer to buffer */
int nByte, /* Number of bytes to copy */
int eOp, /* 0 -> copy from page, 1 -> copy to page */
DbPage *pDbPage /* Page containing pPayload */
){
if( eOp ){
/* Copy data from buffer to page (a write operation) */
int rc = sqlite3PagerWrite(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
memcpy(pPayload, pBuf, nByte);
}else{
/* Copy data from page to buffer (a read operation) */
memcpy(pBuf, pPayload, nByte);
}
return SQLITE_OK;
}
/*
** This function is used to read or overwrite payload information
** for the entry that the pCur cursor is pointing to. The eOp
** argument is interpreted as follows:
**
** 0: The operation is a read. Populate the overflow cache.
** 1: The operation is a write. Populate the overflow cache.
**
** A total of "amt" bytes are read or written beginning at "offset".
** Data is read to or from the buffer pBuf.
**
** The content being read or written might appear on the main page
** or be scattered out on multiple overflow pages.
**
** If the current cursor entry uses one or more overflow pages
** this function may allocate space for and lazily populate
** the overflow page-list cache array (BtCursor.aOverflow).
** Subsequent calls use this cache to make seeking to the supplied offset
** more efficient.
**
** Once an overflow page-list cache has been allocated, it must be
** invalidated if some other cursor writes to the same table, or if
** the cursor is moved to a different row. Additionally, in auto-vacuum
** mode, the following events may invalidate an overflow page-list cache.
**
** * An incremental vacuum,
** * A commit in auto_vacuum="full" mode,
** * Creating a table (may require moving an overflow page).
*/
static int accessPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
u32 offset, /* Begin reading this far into payload */
u32 amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int eOp /* zero to read. non-zero to write. */
){
unsigned char *aPayload;
int rc = SQLITE_OK;
int iIdx = 0;
MemPage *pPage = pCur->pPage; /* Btree page of current entry */
BtShared *pBt = pCur->pBt; /* Btree this cursor belongs to */
#ifdef SQLITE_DIRECT_OVERFLOW_READ
unsigned char * const pBufStart = pBuf; /* Start of original out buffer */
#endif
assert( pPage );
assert( eOp==0 || eOp==1 );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->ix<pPage->nCell );
assert( cursorHoldsMutex(pCur) );
getCellInfo(pCur);
aPayload = pCur->info.pPayload;
assert( offset+amt <= pCur->info.nPayload );
assert( aPayload > pPage->aData );
if( (uptr)(aPayload - pPage->aData) > (pBt->usableSize - pCur->info.nLocal) ){
/* Trying to read or write past the end of the data is an error. The
** conditional above is really:
** &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
** but is recast into its current form to avoid integer overflow problems
*/
return SQLITE_CORRUPT_PAGE(pPage);
}
/* Check if data must be read/written to/from the btree page itself. */
if( offset<pCur->info.nLocal ){
int a = amt;
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
offset = 0;
pBuf += a;
amt -= a;
}else{
offset -= pCur->info.nLocal;
}
if( rc==SQLITE_OK && amt>0 ){
const u32 ovflSize = pBt->usableSize - 4; /* Bytes content per ovfl page */
Pgno nextPage;
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
/* If the BtCursor.aOverflow[] has not been allocated, allocate it now.
**
** The aOverflow[] array is sized at one entry for each overflow page
** in the overflow chain. The page number of the first overflow page is
** stored in aOverflow[0], etc. A value of 0 in the aOverflow[] array
** means "not yet known" (the cache is lazily populated).
*/
if( (pCur->curFlags & BTCF_ValidOvfl)==0 ){
int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
if( pCur->aOverflow==0
|| nOvfl*(int)sizeof(Pgno) > sqlite3MallocSize(pCur->aOverflow)
){
Pgno *aNew = (Pgno*)sqlite3Realloc(
pCur->aOverflow, nOvfl*2*sizeof(Pgno)
);
if( aNew==0 ){
return SQLITE_NOMEM_BKPT;
}else{
pCur->aOverflow = aNew;
}
}
memset(pCur->aOverflow, 0, nOvfl*sizeof(Pgno));
pCur->curFlags |= BTCF_ValidOvfl;
}else{
/* If the overflow page-list cache has been allocated and the
** entry for the first required overflow page is valid, skip
** directly to it.
*/
if( pCur->aOverflow[offset/ovflSize] ){
iIdx = (offset/ovflSize);
nextPage = pCur->aOverflow[iIdx];
offset = (offset%ovflSize);
}
}
assert( rc==SQLITE_OK && amt>0 );
while( nextPage ){
/* If required, populate the overflow page-list cache. */
if( nextPage > pBt->nPage ) return SQLITE_CORRUPT_BKPT;
assert( pCur->aOverflow[iIdx]==0
|| pCur->aOverflow[iIdx]==nextPage
|| CORRUPT_DB );
pCur->aOverflow[iIdx] = nextPage;
if( offset>=ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. The page
** data is not required. So first try to lookup the overflow
** page-list cache, if any, then fall back to the getOverflowPage()
** function.
*/
assert( pCur->curFlags & BTCF_ValidOvfl );
assert( pCur->pBtree->db==pBt->db );
if( pCur->aOverflow[iIdx+1] ){
nextPage = pCur->aOverflow[iIdx+1];
}else{
rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
}
offset -= ovflSize;
}else{
/* Need to read this page properly. It contains some of the
** range of data that is being read (eOp==0) or written (eOp!=0).
*/
int a = amt;
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
#ifdef SQLITE_DIRECT_OVERFLOW_READ
/* If all the following are true:
**
** 1) this is a read operation, and
** 2) data is required from the start of this overflow page, and
** 3) there are no dirty pages in the page-cache
** 4) the database is file-backed, and
** 5) the page is not in the WAL file
** 6) at least 4 bytes have already been read into the output buffer
**
** then data can be read directly from the database file into the
** output buffer, bypassing the page-cache altogether. This speeds
** up loading large records that span many overflow pages.
*/
if( eOp==0 /* (1) */
&& offset==0 /* (2) */
&& sqlite3PagerDirectReadOk(pBt->pPager, nextPage) /* (3,4,5) */
&& &pBuf[-4]>=pBufStart /* (6) */
){
sqlite3_file *fd = sqlite3PagerFile(pBt->pPager);
u8 aSave[4];
u8 *aWrite = &pBuf[-4];
assert( aWrite>=pBufStart ); /* due to (6) */
memcpy(aSave, aWrite, 4);
rc = sqlite3OsRead(fd, aWrite, a+4, (i64)pBt->pageSize*(nextPage-1));
if( rc && nextPage>pBt->nPage ) rc = SQLITE_CORRUPT_BKPT;
nextPage = get4byte(aWrite);
memcpy(aWrite, aSave, 4);
}else
#endif
{
DbPage *pDbPage;
rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage,
(eOp==0 ? PAGER_GET_READONLY : 0)
);
if( rc==SQLITE_OK ){
aPayload = sqlite3PagerGetData(pDbPage);
nextPage = get4byte(aPayload);
rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
sqlite3PagerUnref(pDbPage);
offset = 0;
}
}
amt -= a;
if( amt==0 ) return rc;
pBuf += a;
}
if( rc ) break;
iIdx++;
}
}
if( rc==SQLITE_OK && amt>0 ){
/* Overflow chain ends prematurely */
return SQLITE_CORRUPT_PAGE(pPage);
}
return rc;
}
/*
** Read part of the payload for the row at which that cursor pCur is currently
** pointing. "amt" bytes will be transferred into pBuf[]. The transfer
** begins at "offset".
**
** pCur can be pointing to either a table or an index b-tree.
** If pointing to a table btree, then the content section is read. If
** pCur is pointing to an index b-tree then the key section is read.
**
** For sqlite3BtreePayload(), the caller must ensure that pCur is pointing
** to a valid row in the table. For sqlite3BtreePayloadChecked(), the
** cursor might be invalid or might need to be restored before being read.
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreePayload(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>=0 && pCur->pPage );
assert( pCur->ix<pCur->pPage->nCell );
return accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
}
/*
** This variant of sqlite3BtreePayload() works even if the cursor has not
** in the CURSOR_VALID state. It is only used by the sqlite3_blob_read()
** interface.
*/
#ifndef SQLITE_OMIT_INCRBLOB
static SQLITE_NOINLINE int accessPayloadChecked(
BtCursor *pCur,
u32 offset,
u32 amt,
void *pBuf
){
int rc;
if ( pCur->eState==CURSOR_INVALID ){
return SQLITE_ABORT;
}
assert( cursorOwnsBtShared(pCur) );
rc = btreeRestoreCursorPosition(pCur);
return rc ? rc : accessPayload(pCur, offset, amt, pBuf, 0);
}
int sqlite3BtreePayloadChecked(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
if( pCur->eState==CURSOR_VALID ){
assert( cursorOwnsBtShared(pCur) );
return accessPayload(pCur, offset, amt, pBuf, 0);
}else{
return accessPayloadChecked(pCur, offset, amt, pBuf);
}
}
#endif /* SQLITE_OMIT_INCRBLOB */
/*
** Return a pointer to payload information from the entry that the
** pCur cursor is pointing to. The pointer is to the beginning of
** the key if index btrees (pPage->intKey==0) and is the data for
** table btrees (pPage->intKey==1). The number of bytes of available
** key/data is written into *pAmt. If *pAmt==0, then the value
** returned will not be a valid pointer.
**
** This routine is an optimization. It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages. When that is so, this routine can be used to access the
** key and data without making a copy. If the key and/or data spills
** onto overflow pages, then accessPayload() must be used to reassemble
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database. The data might change or move the next time
** any btree routine is called.
*/
static const void *fetchPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
u32 *pAmt /* Write the number of available bytes here */
){
int amt;
assert( pCur!=0 && pCur->iPage>=0 && pCur->pPage);
assert( pCur->eState==CURSOR_VALID );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
assert( cursorOwnsBtShared(pCur) );
assert( pCur->ix<pCur->pPage->nCell );
assert( pCur->info.nSize>0 );
assert( pCur->info.pPayload>pCur->pPage->aData || CORRUPT_DB );
assert( pCur->info.pPayload<pCur->pPage->aDataEnd ||CORRUPT_DB);
amt = pCur->info.nLocal;
if( amt>(int)(pCur->pPage->aDataEnd - pCur->info.pPayload) ){
/* There is too little space on the page for the expected amount
** of local content. Database must be corrupt. */
assert( CORRUPT_DB );
amt = MAX(0, (int)(pCur->pPage->aDataEnd - pCur->info.pPayload));
}
*pAmt = (u32)amt;
return (void*)pCur->info.pPayload;
}
/*
** For the entry that cursor pCur is point to, return as
** many bytes of the key or data as are available on the local
** b-tree page. Write the number of available bytes into *pAmt.
**
** The pointer returned is ephemeral. The key/data may move
** or be destroyed on the next call to any Btree routine,
** including calls from other threads against the same cache.
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite3BtreePayloadFetch(BtCursor *pCur, u32 *pAmt){
return fetchPayload(pCur, pAmt);
}
/*
** Move the cursor down to a new child page. The newPgno argument is the
** page number of the child page to move to.
**
** This function returns SQLITE_CORRUPT if the page-header flags field of
** the new child page does not match the flags field of the parent (i.e.
** if an intkey page appears to be the parent of a non-intkey page, or
** vice-versa).
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
BtShared *pBt = pCur->pBt;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
assert( pCur->iPage>=0 );
if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
return SQLITE_CORRUPT_BKPT;
}
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
pCur->aiIdx[pCur->iPage] = pCur->ix;
pCur->apPage[pCur->iPage] = pCur->pPage;
pCur->ix = 0;
pCur->iPage++;
return getAndInitPage(pBt, newPgno, &pCur->pPage, pCur, pCur->curPagerFlags);
}
#ifdef SQLITE_DEBUG
/*
** Page pParent is an internal (non-leaf) tree page. This function
** asserts that page number iChild is the left-child if the iIdx'th
** cell in page pParent. Or, if iIdx is equal to the total number of
** cells in pParent, that page number iChild is the right-child of
** the page.
*/
static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
if( CORRUPT_DB ) return; /* The conditions tested below might not be true
** in a corrupt database */
assert( iIdx<=pParent->nCell );
if( iIdx==pParent->nCell ){
assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
}else{
assert( get4byte(findCell(pParent, iIdx))==iChild );
}
}
#else
# define assertParentIndex(x,y,z)
#endif
/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from. If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
MemPage *pLeaf;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>0 );
assert( pCur->pPage );
assertParentIndex(
pCur->apPage[pCur->iPage-1],
pCur->aiIdx[pCur->iPage-1],
pCur->pPage->pgno
);
testcase( pCur->aiIdx[pCur->iPage-1] > pCur->apPage[pCur->iPage-1]->nCell );
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
pCur->ix = pCur->aiIdx[pCur->iPage-1];
pLeaf = pCur->pPage;
pCur->pPage = pCur->apPage[--pCur->iPage];
releasePageNotNull(pLeaf);
}
/*
** Move the cursor to point to the root page of its b-tree structure.
**
** If the table has a virtual root page, then the cursor is moved to point
** to the virtual root page instead of the actual root page. A table has a
** virtual root page when the actual root page contains no cells and a
** single child page. This can only happen with the table rooted at page 1.
**
** If the b-tree structure is empty, the cursor state is set to
** CURSOR_INVALID and this routine returns SQLITE_EMPTY. Otherwise,
** the cursor is set to point to the first cell located on the root
** (or virtual root) page and the cursor state is set to CURSOR_VALID.
**
** If this function returns successfully, it may be assumed that the
** page-header flags indicate that the [virtual] root-page is the expected
** kind of b-tree page (i.e. if when opening the cursor the caller did not
** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
** indicating a table b-tree, or if the caller did specify a KeyInfo
** structure the flags byte is set to 0x02 or 0x0A, indicating an index
** b-tree).
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pRoot;
int rc = SQLITE_OK;
assert( cursorOwnsBtShared(pCur) );
assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
assert( CURSOR_VALID < CURSOR_REQUIRESEEK );
assert( CURSOR_FAULT > CURSOR_REQUIRESEEK );
assert( pCur->eState < CURSOR_REQUIRESEEK || pCur->iPage<0 );
assert( pCur->pgnoRoot>0 || pCur->iPage<0 );
if( pCur->iPage>=0 ){
if( pCur->iPage ){
releasePageNotNull(pCur->pPage);
while( --pCur->iPage ){
releasePageNotNull(pCur->apPage[pCur->iPage]);
}
pCur->pPage = pCur->apPage[0];
goto skip_init;
}
}else if( pCur->pgnoRoot==0 ){
pCur->eState = CURSOR_INVALID;
return SQLITE_EMPTY;
}else{
assert( pCur->iPage==(-1) );
if( pCur->eState>=CURSOR_REQUIRESEEK ){
if( pCur->eState==CURSOR_FAULT ){
assert( pCur->skipNext!=SQLITE_OK );
return pCur->skipNext;
}
sqlite3BtreeClearCursor(pCur);
}
rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->pPage,
0, pCur->curPagerFlags);
if( rc!=SQLITE_OK ){
pCur->eState = CURSOR_INVALID;
return rc;
}
pCur->iPage = 0;
pCur->curIntKey = pCur->pPage->intKey;
}
pRoot = pCur->pPage;
assert( pRoot->pgno==pCur->pgnoRoot );
/* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
** NULL, the caller expects a table b-tree. If this is not the case,
** return an SQLITE_CORRUPT error.
**
** Earlier versions of SQLite assumed that this test could not fail
** if the root page was already loaded when this function was called (i.e.
** if pCur->iPage>=0). But this is not so if the database is corrupted
** in such a way that page pRoot is linked into a second b-tree table
** (or the freelist). */
assert( pRoot->intKey==1 || pRoot->intKey==0 );
if( pRoot->isInit==0 || (pCur->pKeyInfo==0)!=pRoot->intKey ){
return SQLITE_CORRUPT_PAGE(pCur->pPage);
}
skip_init:
pCur->ix = 0;
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidNKey|BTCF_ValidOvfl);
pRoot = pCur->pPage;
if( pRoot->nCell>0 ){
pCur->eState = CURSOR_VALID;
}else if( !pRoot->leaf ){
Pgno subpage;
if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
pCur->eState = CURSOR_VALID;
rc = moveToChild(pCur, subpage);
}else{
pCur->eState = CURSOR_INVALID;
rc = SQLITE_EMPTY;
}
return rc;
}
/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
**
** The left-most leaf is the one with the smallest key - the first
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
assert( pCur->ix<pPage->nCell );
pgno = get4byte(findCell(pPage, pCur->ix));
rc = moveToChild(pCur, pgno);
}
return rc;
}
/*
** Move the cursor down to the right-most leaf entry beneath the
** page to which it is currently pointing. Notice the difference
** between moveToLeftmost() and moveToRightmost(). moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
**
** The right-most entry is the one with the largest key - the last
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage = 0;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( !(pPage = pCur->pPage)->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
pCur->ix = pPage->nCell;
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
pCur->ix = pPage->nCell-1;
assert( pCur->info.nSize==0 );
assert( (pCur->curFlags & BTCF_ValidNKey)==0 );
return SQLITE_OK;
}
/* Move the cursor to the first entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
int rc;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
assert( pCur->pPage->nCell>0 );
*pRes = 0;
rc = moveToLeftmost(pCur);
}else if( rc==SQLITE_EMPTY ){
assert( pCur->pgnoRoot==0 || pCur->pPage->nCell==0 );
*pRes = 1;
rc = SQLITE_OK;
}
return rc;
}
/* Move the cursor to the last entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
int rc;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
/* If the cursor already points to the last entry, this is a no-op. */
if( CURSOR_VALID==pCur->eState && (pCur->curFlags & BTCF_AtLast)!=0 ){
#ifdef SQLITE_DEBUG
/* This block serves to assert() that the cursor really does point
** to the last entry in the b-tree. */
int ii;
for(ii=0; ii<pCur->iPage; ii++){
assert( pCur->aiIdx[ii]==pCur->apPage[ii]->nCell );
}
assert( pCur->ix==pCur->pPage->nCell-1 );
assert( pCur->pPage->leaf );
#endif
*pRes = 0;
return SQLITE_OK;
}
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
if( rc==SQLITE_OK ){
pCur->curFlags |= BTCF_AtLast;
}else{
pCur->curFlags &= ~BTCF_AtLast;
}
}else if( rc==SQLITE_EMPTY ){
assert( pCur->pgnoRoot==0 || pCur->pPage->nCell==0 );
*pRes = 1;
rc = SQLITE_OK;
}
return rc;
}
/* Move the cursor so that it points to an entry near the key
** specified by pIdxKey or intKey. Return a success code.
**
** For INTKEY tables, the intKey parameter is used. pIdxKey
** must be NULL. For index tables, pIdxKey is used and intKey
** is ignored.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
**
** An integer is written into *pRes which is the result of
** comparing the key with the entry to which the cursor is
** pointing. The meaning of the integer written into
** *pRes is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than intKey/pIdxKey or if the table is empty
** and the cursor is therefore left point to nothing.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches intKey/pIdxKey.
**
** *pRes>0 The cursor is left pointing at an entry that
** is larger than intKey/pIdxKey.
**
** For index tables, the pIdxKey->eqSeen field is set to 1 if there
** exists an entry in the table that exactly matches pIdxKey.
*/
int sqlite3BtreeMovetoUnpacked(
BtCursor *pCur, /* The cursor to be moved */
UnpackedRecord *pIdxKey, /* Unpacked index key */
i64 intKey, /* The table key */
int biasRight, /* If true, bias the search to the high end */
int *pRes /* Write search results here */
){
int rc;
RecordCompare xRecordCompare;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
assert( pRes );
assert( (pIdxKey==0)==(pCur->pKeyInfo==0) );
assert( pCur->eState!=CURSOR_VALID || (pIdxKey==0)==(pCur->curIntKey!=0) );
/* If the cursor is already positioned at the point we are trying
** to move to, then just return without doing any work */
if( pIdxKey==0
&& pCur->eState==CURSOR_VALID && (pCur->curFlags & BTCF_ValidNKey)!=0
){
if( pCur->info.nKey==intKey ){
*pRes = 0;
return SQLITE_OK;
}
if( pCur->info.nKey<intKey ){
if( (pCur->curFlags & BTCF_AtLast)!=0 ){
*pRes = -1;
return SQLITE_OK;
}
/* If the requested key is one more than the previous key, then
** try to get there using sqlite3BtreeNext() rather than a full
** binary search. This is an optimization only. The correct answer
** is still obtained without this case, only a little more slowely */
if( pCur->info.nKey+1==intKey ){
*pRes = 0;
rc = sqlite3BtreeNext(pCur, 0);
if( rc==SQLITE_OK ){
getCellInfo(pCur);
if( pCur->info.nKey==intKey ){
return SQLITE_OK;
}
}else if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
}else{
return rc;
}
}
}
}
#ifdef SQLITE_DEBUG
pCur->pBtree->nSeek++; /* Performance measurement during testing */
#endif
if( pIdxKey ){
xRecordCompare = sqlite3VdbeFindCompare(pIdxKey);
pIdxKey->errCode = 0;
assert( pIdxKey->default_rc==1
|| pIdxKey->default_rc==0
|| pIdxKey->default_rc==-1
);
}else{
xRecordCompare = 0; /* All keys are integers */
}
rc = moveToRoot(pCur);
if( rc ){
if( rc==SQLITE_EMPTY ){
assert( pCur->pgnoRoot==0 || pCur->pPage->nCell==0 );
*pRes = -1;
return SQLITE_OK;
}
return rc;
}
assert( pCur->pPage );
assert( pCur->pPage->isInit );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->pPage->nCell > 0 );
assert( pCur->iPage==0 || pCur->apPage[0]->intKey==pCur->curIntKey );
assert( pCur->curIntKey || pIdxKey );
for(;;){
int lwr, upr, idx, c;
Pgno chldPg;
MemPage *pPage = pCur->pPage;
u8 *pCell; /* Pointer to current cell in pPage */
/* pPage->nCell must be greater than zero. If this is the root-page
** the cursor would have been INVALID above and this for(;;) loop
** not run. If this is not the root-page, then the moveToChild() routine
** would have already detected db corruption. Similarly, pPage must
** be the right kind (index or table) of b-tree page. Otherwise
** a moveToChild() or moveToRoot() call would have detected corruption. */
assert( pPage->nCell>0 );
assert( pPage->intKey==(pIdxKey==0) );
lwr = 0;
upr = pPage->nCell-1;
assert( biasRight==0 || biasRight==1 );
idx = upr>>(1-biasRight); /* idx = biasRight ? upr : (lwr+upr)/2; */
pCur->ix = (u16)idx;
if( xRecordCompare==0 ){
for(;;){
i64 nCellKey;
pCell = findCellPastPtr(pPage, idx);
if( pPage->intKeyLeaf ){
while( 0x80 <= *(pCell++) ){
if( pCell>=pPage->aDataEnd ){
return SQLITE_CORRUPT_PAGE(pPage);
}
}
}
getVarint(pCell, (u64*)&nCellKey);
if( nCellKey<intKey ){
lwr = idx+1;
if( lwr>upr ){ c = -1; break; }
}else if( nCellKey>intKey ){
upr = idx-1;
if( lwr>upr ){ c = +1; break; }
}else{
assert( nCellKey==intKey );
pCur->ix = (u16)idx;
if( !pPage->leaf ){
lwr = idx;
goto moveto_next_layer;
}else{
pCur->curFlags |= BTCF_ValidNKey;
pCur->info.nKey = nCellKey;
pCur->info.nSize = 0;
*pRes = 0;
return SQLITE_OK;
}
}
assert( lwr+upr>=0 );
idx = (lwr+upr)>>1; /* idx = (lwr+upr)/2; */
}
}else{
for(;;){
int nCell; /* Size of the pCell cell in bytes */
pCell = findCellPastPtr(pPage, idx);
/* The maximum supported page-size is 65536 bytes. This means that
** the maximum number of record bytes stored on an index B-Tree
** page is less than 16384 bytes and may be stored as a 2-byte
** varint. This information is used to attempt to avoid parsing
** the entire cell by checking for the cases where the record is
** stored entirely within the b-tree page by inspecting the first
** 2 bytes of the cell.
*/
nCell = pCell[0];
if( nCell<=pPage->max1bytePayload ){
/* This branch runs if the record-size field of the cell is a
** single byte varint and the record fits entirely on the main
** b-tree page. */
testcase( pCell+nCell+1==pPage->aDataEnd );
c = xRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
}else if( !(pCell[1] & 0x80)
&& (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
){
/* The record-size field is a 2 byte varint and the record
** fits entirely on the main b-tree page. */
testcase( pCell+nCell+2==pPage->aDataEnd );
c = xRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
}else{
/* The record flows over onto one or more overflow pages. In
** this case the whole cell needs to be parsed, a buffer allocated
** and accessPayload() used to retrieve the record into the
** buffer before VdbeRecordCompare() can be called.
**
** If the record is corrupt, the xRecordCompare routine may read
** up to two varints past the end of the buffer. An extra 18
** bytes of padding is allocated at the end of the buffer in
** case this happens. */
void *pCellKey;
u8 * const pCellBody = pCell - pPage->childPtrSize;
const int nOverrun = 18; /* Size of the overrun padding */
pPage->xParseCell(pPage, pCellBody, &pCur->info);
nCell = (int)pCur->info.nKey;
testcase( nCell<0 ); /* True if key size is 2^32 or more */
testcase( nCell==0 ); /* Invalid key size: 0x80 0x80 0x00 */
testcase( nCell==1 ); /* Invalid key size: 0x80 0x80 0x01 */
testcase( nCell==2 ); /* Minimum legal index key size */
if( nCell<2 || nCell/pCur->pBt->usableSize>pCur->pBt->nPage ){
rc = SQLITE_CORRUPT_PAGE(pPage);
goto moveto_finish;
}
pCellKey = sqlite3Malloc( nCell+nOverrun );
if( pCellKey==0 ){
rc = SQLITE_NOMEM_BKPT;
goto moveto_finish;
}
pCur->ix = (u16)idx;
rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 0);
memset(((u8*)pCellKey)+nCell,0,nOverrun); /* Fix uninit warnings */
pCur->curFlags &= ~BTCF_ValidOvfl;
if( rc ){
sqlite3_free(pCellKey);
goto moveto_finish;
}
c = sqlite3VdbeRecordCompare(nCell, pCellKey, pIdxKey);
sqlite3_free(pCellKey);
}
assert(
(pIdxKey->errCode!=SQLITE_CORRUPT || c==0)
&& (pIdxKey->errCode!=SQLITE_NOMEM || pCur->pBtree->db->mallocFailed)
);
if( c<0 ){
lwr = idx+1;
}else if( c>0 ){
upr = idx-1;
}else{
assert( c==0 );
*pRes = 0;
rc = SQLITE_OK;
pCur->ix = (u16)idx;
if( pIdxKey->errCode ) rc = SQLITE_CORRUPT_BKPT;
goto moveto_finish;
}
if( lwr>upr ) break;
assert( lwr+upr>=0 );
idx = (lwr+upr)>>1; /* idx = (lwr+upr)/2 */
}
}
assert( lwr==upr+1 || (pPage->intKey && !pPage->leaf) );
assert( pPage->isInit );
if( pPage->leaf ){
assert( pCur->ix<pCur->pPage->nCell );
pCur->ix = (u16)idx;
*pRes = c;
rc = SQLITE_OK;
goto moveto_finish;
}
moveto_next_layer:
if( lwr>=pPage->nCell ){
chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
}else{
chldPg = get4byte(findCell(pPage, lwr));
}
pCur->ix = (u16)lwr;
rc = moveToChild(pCur, chldPg);
if( rc ) break;
}
moveto_finish:
pCur->info.nSize = 0;
assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
return rc;
}
/*
** Return TRUE if the cursor is not pointing at an entry of the table.
**
** TRUE will be returned after a call to sqlite3BtreeNext() moves
** past the last entry in the table or sqlite3BtreePrev() moves past
** the first entry. TRUE is also returned if the table is empty.
*/
int sqlite3BtreeEof(BtCursor *pCur){
/* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
** have been deleted? This API will need to change to return an error code
** as well as the boolean result value.
*/
return (CURSOR_VALID!=pCur->eState);
}
/*
** Return an estimate for the number of rows in the table that pCur is
** pointing to. Return a negative number if no estimate is currently
** available.
*/
i64 sqlite3BtreeRowCountEst(BtCursor *pCur){
i64 n;
u8 i;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
/* Currently this interface is only called by the OP_IfSmaller
** opcode, and it that case the cursor will always be valid and
** will always point to a leaf node. */
if( NEVER(pCur->eState!=CURSOR_VALID) ) return -1;
if( NEVER(pCur->pPage->leaf==0) ) return -1;
n = pCur->pPage->nCell;
for(i=0; i<pCur->iPage; i++){
n *= pCur->apPage[i]->nCell;
}
return n;
}
/*
** Advance the cursor to the next entry in the database.
** Return value:
**
** SQLITE_OK success
** SQLITE_DONE cursor is already pointing at the last element
** otherwise some kind of error occurred
**
** The main entry point is sqlite3BtreeNext(). That routine is optimized
** for the common case of merely incrementing the cell counter BtCursor.aiIdx
** to the next cell on the current page. The (slower) btreeNext() helper
** routine is called when it is necessary to move to a different page or
** to restore the cursor.
**
** If bit 0x01 of the F argument in sqlite3BtreeNext(C,F) is 1, then the
** cursor corresponds to an SQL index and this routine could have been
** skipped if the SQL index had been a unique index. The F argument
** is a hint to the implement. SQLite btree implementation does not use
** this hint, but COMDB2 does.
*/
static SQLITE_NOINLINE int btreeNext(BtCursor *pCur){
int rc;
int idx;
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
if( pCur->eState!=CURSOR_VALID ){
assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
rc = restoreCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
if( CURSOR_INVALID==pCur->eState ){
return SQLITE_DONE;
}
if( pCur->eState==CURSOR_SKIPNEXT ){
pCur->eState = CURSOR_VALID;
if( pCur->skipNext>0 ) return SQLITE_OK;
}
}
pPage = pCur->pPage;
idx = ++pCur->ix;
if( !pPage->isInit || sqlite3FaultSim(412) ){
/* The only known way for this to happen is for there to be a
** recursive SQL function that does a DELETE operation as part of a
** SELECT which deletes content out from under an active cursor
** in a corrupt database file where the table being DELETE-ed from
** has pages in common with the table being queried. See TH3
** module cov1/btree78.test testcase 220 (2018-06-08) for an
** example. */
return SQLITE_CORRUPT_BKPT;
}
/* If the database file is corrupt, it is possible for the value of idx
** to be invalid here. This can only occur if a second cursor modifies
** the page while cursor pCur is holding a reference to it. Which can
** only happen if the database is corrupt in such a way as to link the
** page into more than one b-tree structure.
**
** Update 2019-12-23: appears to long longer be possible after the
** addition of anotherValidCursor() condition on balance_deeper(). */
harmless( idx>pPage->nCell );
if( idx>=pPage->nCell ){
if( !pPage->leaf ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
if( rc ) return rc;
return moveToLeftmost(pCur);
}
do{
if( pCur->iPage==0 ){
pCur->eState = CURSOR_INVALID;
return SQLITE_DONE;
}
moveToParent(pCur);
pPage = pCur->pPage;
}while( pCur->ix>=pPage->nCell );
if( pPage->intKey ){
return sqlite3BtreeNext(pCur, 0);
}else{
return SQLITE_OK;
}
}
if( pPage->leaf ){
return SQLITE_OK;
}else{
return moveToLeftmost(pCur);
}
}
int sqlite3BtreeNext(BtCursor *pCur, int flags){
MemPage *pPage;
UNUSED_PARAMETER( flags ); /* Used in COMDB2 but not native SQLite */
assert( cursorOwnsBtShared(pCur) );
assert( flags==0 || flags==1 );
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur);
pPage = pCur->pPage;
if( (++pCur->ix)>=pPage->nCell ){
pCur->ix--;
return btreeNext(pCur);
}
if( pPage->leaf ){
return SQLITE_OK;
}else{
return moveToLeftmost(pCur);
}
}
/*
** Step the cursor to the back to the previous entry in the database.
** Return values:
**
** SQLITE_OK success
** SQLITE_DONE the cursor is already on the first element of the table
** otherwise some kind of error occurred
**
** The main entry point is sqlite3BtreePrevious(). That routine is optimized
** for the common case of merely decrementing the cell counter BtCursor.aiIdx
** to the previous cell on the current page. The (slower) btreePrevious()
** helper routine is called when it is necessary to move to a different page
** or to restore the cursor.
**
** If bit 0x01 of the F argument to sqlite3BtreePrevious(C,F) is 1, then
** the cursor corresponds to an SQL index and this routine could have been
** skipped if the SQL index had been a unique index. The F argument is a
** hint to the implement. The native SQLite btree implementation does not
** use this hint, but COMDB2 does.
*/
static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur){
int rc;
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
assert( pCur->info.nSize==0 );
if( pCur->eState!=CURSOR_VALID ){
rc = restoreCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
if( CURSOR_INVALID==pCur->eState ){
return SQLITE_DONE;
}
if( CURSOR_SKIPNEXT==pCur->eState ){
pCur->eState = CURSOR_VALID;
if( pCur->skipNext<0 ) return SQLITE_OK;
}
}
pPage = pCur->pPage;
assert( pPage->isInit );
if( !pPage->leaf ){
int idx = pCur->ix;
rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
if( rc ) return rc;
rc = moveToRightmost(pCur);
}else{
while( pCur->ix==0 ){
if( pCur->iPage==0 ){
pCur->eState = CURSOR_INVALID;
return SQLITE_DONE;
}
moveToParent(pCur);
}
assert( pCur->info.nSize==0 );
assert( (pCur->curFlags & (BTCF_ValidOvfl))==0 );
pCur->ix--;
pPage = pCur->pPage;
if( pPage->intKey && !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, 0);
}else{
rc = SQLITE_OK;
}
}
return rc;
}
int sqlite3BtreePrevious(BtCursor *pCur, int flags){
assert( cursorOwnsBtShared(pCur) );
assert( flags==0 || flags==1 );
UNUSED_PARAMETER( flags ); /* Used in COMDB2 but not native SQLite */
pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
pCur->info.nSize = 0;
if( pCur->eState!=CURSOR_VALID
|| pCur->ix==0
|| pCur->pPage->leaf==0
){
return btreePrevious(pCur);
}
pCur->ix--;
return SQLITE_OK;
}
/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty. (In other words, sqlite3PagerWrite()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3PagerUnref() on the new page when it is done.
**
** SQLITE_OK is returned on success. Any other return value indicates
** an error. *ppPage is set to NULL in the event of an error.
**
** If the "nearby" parameter is not 0, then an effort is made to
** locate a page close to the page number "nearby". This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
**
** If the eMode parameter is BTALLOC_EXACT and the nearby page exists
** anywhere on the free-list, then it is guaranteed to be returned. If
** eMode is BTALLOC_LT then the page returned will be less than or equal
** to nearby if any such page exists. If eMode is BTALLOC_ANY then there
** are no restrictions on which page is returned.
*/
static int allocateBtreePage(
BtShared *pBt, /* The btree */
MemPage **ppPage, /* Store pointer to the allocated page here */
Pgno *pPgno, /* Store the page number here */
Pgno nearby, /* Search for a page near this one */
u8 eMode /* BTALLOC_EXACT, BTALLOC_LT, or BTALLOC_ANY */
){
MemPage *pPage1;
int rc;
u32 n; /* Number of pages on the freelist */
u32 k; /* Number of leaves on the trunk of the freelist */
MemPage *pTrunk = 0;
MemPage *pPrevTrunk = 0;
Pgno mxPage; /* Total size of the database file */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( eMode==BTALLOC_ANY || (nearby>0 && IfNotOmitAV(pBt->autoVacuum)) );
pPage1 = pBt->pPage1;
mxPage = btreePagecount(pBt);
/* EVIDENCE-OF: R-05119-02637 The 4-byte big-endian integer at offset 36
** stores stores the total number of pages on the freelist. */
n = get4byte(&pPage1->aData[36]);
testcase( n==mxPage-1 );
if( n>=mxPage ){
return SQLITE_CORRUPT_BKPT;
}
if( n>0 ){
/* There are pages on the freelist. Reuse one of those pages. */
Pgno iTrunk;
u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
u32 nSearch = 0; /* Count of the number of search attempts */
/* If eMode==BTALLOC_EXACT and a query of the pointer-map
** shows that the page 'nearby' is somewhere on the free-list, then
** the entire-list will be searched for that page.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
if( eMode==BTALLOC_EXACT ){
if( nearby<=mxPage ){
u8 eType;
assert( nearby>0 );
assert( pBt->autoVacuum );
rc = ptrmapGet(pBt, nearby, &eType, 0);
if( rc ) return rc;
if( eType==PTRMAP_FREEPAGE ){
searchList = 1;
}
}
}else if( eMode==BTALLOC_LE ){
searchList = 1;
}
#endif
/* Decrement the free-list count by 1. Set iTrunk to the index of the
** first free-list trunk page. iPrevTrunk is initially 1.
*/
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) return rc;
put4byte(&pPage1->aData[36], n-1);
/* The code within this loop is run only once if the 'searchList' variable
** is not true. Otherwise, it runs once for each trunk-page on the
** free-list until the page 'nearby' is located (eMode==BTALLOC_EXACT)
** or until a page less than 'nearby' is located (eMode==BTALLOC_LT)
*/
do {
pPrevTrunk = pTrunk;
if( pPrevTrunk ){
/* EVIDENCE-OF: R-01506-11053 The first integer on a freelist trunk page
** is the page number of the next freelist trunk page in the list or
** zero if this is the last freelist trunk page. */
iTrunk = get4byte(&pPrevTrunk->aData[0]);
}else{
/* EVIDENCE-OF: R-59841-13798 The 4-byte big-endian integer at offset 32
** stores the page number of the first page of the freelist, or zero if
** the freelist is empty. */
iTrunk = get4byte(&pPage1->aData[32]);
}
testcase( iTrunk==mxPage );
if( iTrunk>mxPage || nSearch++ > n ){
rc = SQLITE_CORRUPT_PGNO(pPrevTrunk ? pPrevTrunk->pgno : 1);
}else{
rc = btreeGetUnusedPage(pBt, iTrunk, &pTrunk, 0);
}
if( rc ){
pTrunk = 0;
goto end_allocate_page;
}
assert( pTrunk!=0 );
assert( pTrunk->aData!=0 );
/* EVIDENCE-OF: R-13523-04394 The second integer on a freelist trunk page
** is the number of leaf page pointers to follow. */
k = get4byte(&pTrunk->aData[4]);
if( k==0 && !searchList ){
/* The trunk has no leaves and the list is not being searched.
** So extract the trunk page itself and use it as the newly
** allocated page */
assert( pPrevTrunk==0 );
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
*pPgno = iTrunk;
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
*ppPage = pTrunk;
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
}else if( k>(u32)(pBt->usableSize/4 - 2) ){
/* Value of k is out of range. Database corruption */
rc = SQLITE_CORRUPT_PGNO(iTrunk);
goto end_allocate_page;
#ifndef SQLITE_OMIT_AUTOVACUUM
}else if( searchList
&& (nearby==iTrunk || (iTrunk<nearby && eMode==BTALLOC_LE))
){
/* The list is being searched and this trunk page is the page
** to allocate, regardless of whether it has leaves.
*/
*pPgno = iTrunk;
*ppPage = pTrunk;
searchList = 0;
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
if( k==0 ){
if( !pPrevTrunk ){
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
}else{
rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
}
}else{
/* The trunk page is required by the caller but it contains
** pointers to free-list leaves. The first leaf becomes a trunk
** page in this case.
*/
MemPage *pNewTrunk;
Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
if( iNewTrunk>mxPage ){
rc = SQLITE_CORRUPT_PGNO(iTrunk);
goto end_allocate_page;
}
testcase( iNewTrunk==mxPage );
rc = btreeGetUnusedPage(pBt, iNewTrunk, &pNewTrunk, 0);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pNewTrunk);
goto end_allocate_page;
}
memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
put4byte(&pNewTrunk->aData[4], k-1);
memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
releasePage(pNewTrunk);
if( !pPrevTrunk ){
assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
put4byte(&pPage1->aData[32], iNewTrunk);
}else{
rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
put4byte(&pPrevTrunk->aData[0], iNewTrunk);
}
}
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
#endif
}else if( k>0 ){
/* Extract a leaf from the trunk */
u32 closest;
Pgno iPage;
unsigned char *aData = pTrunk->aData;
if( nearby>0 ){
u32 i;
closest = 0;
if( eMode==BTALLOC_LE ){
for(i=0; i<k; i++){
iPage = get4byte(&aData[8+i*4]);
if( iPage<=nearby ){
closest = i;
break;
}
}
}else{
int dist;
dist = sqlite3AbsInt32(get4byte(&aData[8]) - nearby);
for(i=1; i<k; i++){
int d2 = sqlite3AbsInt32(get4byte(&aData[8+i*4]) - nearby);
if( d2<dist ){
closest = i;
dist = d2;
}
}
}
}else{
closest = 0;
}
iPage = get4byte(&aData[8+closest*4]);
testcase( iPage==mxPage );
if( iPage>mxPage ){
rc = SQLITE_CORRUPT_PGNO(iTrunk);
goto end_allocate_page;
}
testcase( iPage==mxPage );
if( !searchList
|| (iPage==nearby || (iPage<nearby && eMode==BTALLOC_LE))
){
int noContent;
*pPgno = iPage;
TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
": %d more free pages\n",
*pPgno, closest+1, k, pTrunk->pgno, n-1));
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ) goto end_allocate_page;
if( closest<k-1 ){
memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
}
put4byte(&aData[4], k-1);
noContent = !btreeGetHasContent(pBt, *pPgno)? PAGER_GET_NOCONTENT : 0;
rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, noContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
*ppPage = 0;
}
}
searchList = 0;
}
}
releasePage(pPrevTrunk);
pPrevTrunk = 0;
}while( searchList );
}else{
/* There are no pages on the freelist, so append a new page to the
** database image.
**
** Normally, new pages allocated by this block can be requested from the
** pager layer with the 'no-content' flag set. This prevents the pager
** from trying to read the pages content from disk. However, if the
** current transaction has already run one or more incremental-vacuum
** steps, then the page we are about to allocate may contain content
** that is required in the event of a rollback. In this case, do
** not set the no-content flag. This causes the pager to load and journal
** the current page content before overwriting it.
**
** Note that the pager will not actually attempt to load or journal
** content for any page that really does lie past the end of the database
** file on disk. So the effects of disabling the no-content optimization
** here are confined to those pages that lie between the end of the
** database image and the end of the database file.
*/
int bNoContent = (0==IfNotOmitAV(pBt->bDoTruncate))? PAGER_GET_NOCONTENT:0;
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc ) return rc;
pBt->nPage++;
if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
/* If *pPgno refers to a pointer-map page, allocate two new pages
** at the end of the file instead of one. The first allocated page
** becomes a new pointer-map page, the second is used by the caller.
*/
MemPage *pPg = 0;
TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetUnusedPage(pBt, pBt->nPage, &pPg, bNoContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pPg->pDbPage);
releasePage(pPg);
}
if( rc ) return rc;
pBt->nPage++;
if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
}
#endif
put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
*pPgno = pBt->nPage;
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, bNoContent);
if( rc ) return rc;
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
*ppPage = 0;
}
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
assert( CORRUPT_DB || *pPgno!=PENDING_BYTE_PAGE(pBt) );
end_allocate_page:
releasePage(pTrunk);
releasePage(pPrevTrunk);
assert( rc!=SQLITE_OK || sqlite3PagerPageRefcount((*ppPage)->pDbPage)<=1 );
assert( rc!=SQLITE_OK || (*ppPage)->isInit==0 );
return rc;
}
/*
** This function is used to add page iPage to the database file free-list.
** It is assumed that the page is not already a part of the free-list.
**
** The value passed as the second argument to this function is optional.
** If the caller happens to have a pointer to the MemPage object
** corresponding to page iPage handy, it may pass it as the second value.
** Otherwise, it may pass NULL.
**
** If a pointer to a MemPage object is passed as the second argument,
** its reference count is not altered by this function.
*/
static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
MemPage *pTrunk = 0; /* Free-list trunk page */
Pgno iTrunk = 0; /* Page number of free-list trunk page */
MemPage *pPage1 = pBt->pPage1; /* Local reference to page 1 */
MemPage *pPage; /* Page being freed. May be NULL. */
int rc; /* Return Code */
u32 nFree; /* Initial number of pages on free-list */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( CORRUPT_DB || iPage>1 );
assert( !pMemPage || pMemPage->pgno==iPage );
if( iPage<2 || iPage>pBt->nPage ){
return SQLITE_CORRUPT_BKPT;
}
if( pMemPage ){
pPage = pMemPage;
sqlite3PagerRef(pPage->pDbPage);
}else{
pPage = btreePageLookup(pBt, iPage);
}
/* Increment the free page count on pPage1 */
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) goto freepage_out;
nFree = get4byte(&pPage1->aData[36]);
put4byte(&pPage1->aData[36], nFree+1);
if( pBt->btsFlags & BTS_SECURE_DELETE ){
/* If the secure_delete option is enabled, then
** always fully overwrite deleted information with zeros.
*/
if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
|| ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
){
goto freepage_out;
}
memset(pPage->aData, 0, pPage->pBt->pageSize);
}
/* If the database supports auto-vacuum, write an entry in the pointer-map
** to indicate that the page is free.
*/
if( ISAUTOVACUUM ){
ptrmapPut(pBt, iPage, PTRMAP_FREEPAGE, 0, &rc);
if( rc ) goto freepage_out;
}
/* Now manipulate the actual database free-list structure. There are two
** possibilities. If the free-list is currently empty, or if the first
** trunk page in the free-list is full, then this page will become a
** new free-list trunk page. Otherwise, it will become a leaf of the
** first trunk page in the current free-list. This block tests if it
** is possible to add the page as a new free-list leaf.
*/
if( nFree!=0 ){
u32 nLeaf; /* Initial number of leaf cells on trunk page */
iTrunk = get4byte(&pPage1->aData[32]);
if( iTrunk>btreePagecount(pBt) ){
rc = SQLITE_CORRUPT_BKPT;
goto freepage_out;
}
rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
if( rc!=SQLITE_OK ){
goto freepage_out;
}
nLeaf = get4byte(&pTrunk->aData[4]);
assert( pBt->usableSize>32 );
if( nLeaf > (u32)pBt->usableSize/4 - 2 ){
rc = SQLITE_CORRUPT_BKPT;
goto freepage_out;
}
if( nLeaf < (u32)pBt->usableSize/4 - 8 ){
/* In this case there is room on the trunk page to insert the page
** being freed as a new leaf.
**
** Note that the trunk page is not really full until it contains
** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
** coded. But due to a coding error in versions of SQLite prior to
** 3.6.0, databases with freelist trunk pages holding more than
** usableSize/4 - 8 entries will be reported as corrupt. In order
** to maintain backwards compatibility with older versions of SQLite,
** we will continue to restrict the number of entries to usableSize/4 - 8
** for now. At some point in the future (once everyone has upgraded
** to 3.6.0 or later) we should consider fixing the conditional above
** to read "usableSize/4-2" instead of "usableSize/4-8".
**
** EVIDENCE-OF: R-19920-11576 However, newer versions of SQLite still
** avoid using the last six entries in the freelist trunk page array in
** order that database files created by newer versions of SQLite can be
** read by older versions of SQLite.
*/
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pTrunk->aData[4], nLeaf+1);
put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
if( pPage && (pBt->btsFlags & BTS_SECURE_DELETE)==0 ){
sqlite3PagerDontWrite(pPage->pDbPage);
}
rc = btreeSetHasContent(pBt, iPage);
}
TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
goto freepage_out;
}
}
/* If control flows to this point, then it was not possible to add the
** the page being freed as a leaf page of the first trunk in the free-list.
** Possibly because the free-list is empty, or possibly because the
** first trunk in the free-list is full. Either way, the page being freed
** will become the new first trunk page in the free-list.
*/
if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
goto freepage_out;
}
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
goto freepage_out;
}
put4byte(pPage->aData, iTrunk);
put4byte(&pPage->aData[4], 0);
put4byte(&pPage1->aData[32], iPage);
TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));
freepage_out:
if( pPage ){
pPage->isInit = 0;
}
releasePage(pPage);
releasePage(pTrunk);
return rc;
}
static void freePage(MemPage *pPage, int *pRC){
if( (*pRC)==SQLITE_OK ){
*pRC = freePage2(pPage->pBt, pPage, pPage->pgno);
}
}
/*
** Free any overflow pages associated with the given Cell. Store
** size information about the cell in pInfo.
*/
static int clearCell(
MemPage *pPage, /* The page that contains the Cell */
unsigned char *pCell, /* First byte of the Cell */
CellInfo *pInfo /* Size information about the cell */
){
BtShared *pBt;
Pgno ovflPgno;
int rc;
int nOvfl;
u32 ovflPageSize;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->xParseCell(pPage, pCell, pInfo);
if( pInfo->nLocal==pInfo->nPayload ){
return SQLITE_OK; /* No overflow pages. Return without doing anything */
}
testcase( pCell + pInfo->nSize == pPage->aDataEnd );
testcase( pCell + (pInfo->nSize-1) == pPage->aDataEnd );
if( pCell + pInfo->nSize > pPage->aDataEnd ){
/* Cell extends past end of page */
return SQLITE_CORRUPT_PAGE(pPage);
}
ovflPgno = get4byte(pCell + pInfo->nSize - 4);
pBt = pPage->pBt;
assert( pBt->usableSize > 4 );
ovflPageSize = pBt->usableSize - 4;
nOvfl = (pInfo->nPayload - pInfo->nLocal + ovflPageSize - 1)/ovflPageSize;
assert( nOvfl>0 ||
(CORRUPT_DB && (pInfo->nPayload + ovflPageSize)<ovflPageSize)
);
while( nOvfl-- ){
Pgno iNext = 0;
MemPage *pOvfl = 0;
if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
/* 0 is not a legal page number and page 1 cannot be an
** overflow page. Therefore if ovflPgno<2 or past the end of the
** file the database must be corrupt. */
return SQLITE_CORRUPT_BKPT;
}
if( nOvfl ){
rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
if( rc ) return rc;
}
if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
&& sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
){
/* There is no reason any cursor should have an outstanding reference
** to an overflow page belonging to a cell that is being deleted/updated.
** So if there exists more than one reference to this page, then it
** must not really be an overflow page and the database must be corrupt.
** It is helpful to detect this before calling freePage2(), as
** freePage2() may zero the page contents if secure-delete mode is
** enabled. If this 'overflow' page happens to be a page that the
** caller is iterating through or using in some other way, this
** can be problematic.
*/
rc = SQLITE_CORRUPT_BKPT;
}else{
rc = freePage2(pBt, pOvfl, ovflPgno);
}
if( pOvfl ){
sqlite3PagerUnref(pOvfl->pDbPage);
}
if( rc ) return rc;
ovflPgno = iNext;
}
return SQLITE_OK;
}
/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[]. Overflow pages are
** allocated and filled in as necessary. The calling procedure
** is responsible for making sure sufficient space has been allocated
** for pCell[].
**
** Note that pCell does not necessary need to point to the pPage->aData
** area. pCell might point to some temporary storage. The cell will
** be constructed in this temporary area then copied into pPage->aData
** later.
*/
static int fillInCell(
MemPage *pPage, /* The page that contains the cell */
unsigned char *pCell, /* Complete text of the cell */
const BtreePayload *pX, /* Payload with which to construct the cell */
int *pnSize /* Write cell size here */
){
int nPayload;
const u8 *pSrc;
int nSrc, n, rc, mn;
int spaceLeft;
MemPage *pToRelease;
unsigned char *pPrior;
unsigned char *pPayload;
BtShared *pBt;
Pgno pgnoOvfl;
int nHeader;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* pPage is not necessarily writeable since pCell might be auxiliary
** buffer space that is separate from the pPage buffer area */
assert( pCell<pPage->aData || pCell>=&pPage->aData[pPage->pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
/* Fill in the header. */
nHeader = pPage->childPtrSize;
if( pPage->intKey ){
nPayload = pX->nData + pX->nZero;
pSrc = pX->pData;
nSrc = pX->nData;
assert( pPage->intKeyLeaf ); /* fillInCell() only called for leaves */
nHeader += putVarint32(&pCell[nHeader], nPayload);
nHeader += putVarint(&pCell[nHeader], *(u64*)&pX->nKey);
}else{
assert( pX->nKey<=0x7fffffff && pX->pKey!=0 );
nSrc = nPayload = (int)pX->nKey;
pSrc = pX->pKey;
nHeader += putVarint32(&pCell[nHeader], nPayload);
}
/* Fill in the payload */
pPayload = &pCell[nHeader];
if( nPayload<=pPage->maxLocal ){
/* This is the common case where everything fits on the btree page
** and no overflow pages are required. */
n = nHeader + nPayload;
testcase( n==3 );
testcase( n==4 );
if( n<4 ) n = 4;
*pnSize = n;
assert( nSrc<=nPayload );
testcase( nSrc<nPayload );
memcpy(pPayload, pSrc, nSrc);
memset(pPayload+nSrc, 0, nPayload-nSrc);
return SQLITE_OK;
}
/* If we reach this point, it means that some of the content will need
** to spill onto overflow pages.
*/
mn = pPage->minLocal;
n = mn + (nPayload - mn) % (pPage->pBt->usableSize - 4);
testcase( n==pPage->maxLocal );
testcase( n==pPage->maxLocal+1 );
if( n > pPage->maxLocal ) n = mn;
spaceLeft = n;
*pnSize = n + nHeader + 4;
pPrior = &pCell[nHeader+n];
pToRelease = 0;
pgnoOvfl = 0;
pBt = pPage->pBt;
/* At this point variables should be set as follows:
**
** nPayload Total payload size in bytes
** pPayload Begin writing payload here
** spaceLeft Space available at pPayload. If nPayload>spaceLeft,
** that means content must spill into overflow pages.
** *pnSize Size of the local cell (not counting overflow pages)
** pPrior Where to write the pgno of the first overflow page
**
** Use a call to btreeParseCellPtr() to verify that the values above
** were computed correctly.
*/
#ifdef SQLITE_DEBUG
{
CellInfo info;
pPage->xParseCell(pPage, pCell, &info);
assert( nHeader==(int)(info.pPayload - pCell) );
assert( info.nKey==pX->nKey );
assert( *pnSize == info.nSize );
assert( spaceLeft == info.nLocal );
}
#endif
/* Write the payload into the local Cell and any extra into overflow pages */
while( 1 ){
n = nPayload;
if( n>spaceLeft ) n = spaceLeft;
/* If pToRelease is not zero than pPayload points into the data area
** of pToRelease. Make sure pToRelease is still writeable. */
assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
/* If pPayload is part of the data area of pPage, then make sure pPage
** is still writeable */
assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
if( nSrc>=n ){
memcpy(pPayload, pSrc, n);
}else if( nSrc>0 ){
n = nSrc;
memcpy(pPayload, pSrc, n);
}else{
memset(pPayload, 0, n);
}
nPayload -= n;
if( nPayload<=0 ) break;
pPayload += n;
pSrc += n;
nSrc -= n;
spaceLeft -= n;
if( spaceLeft==0 ){
MemPage *pOvfl = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
if( pBt->autoVacuum ){
do{
pgnoOvfl++;
} while(
PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt)
);
}
#endif
rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the database supports auto-vacuum, and the second or subsequent
** overflow page is being allocated, add an entry to the pointer-map
** for that page now.
**
** If this is the first overflow page, then write a partial entry
** to the pointer-map. If we write nothing to this pointer-map slot,
** then the optimistic overflow chain processing in clearCell()
** may misinterpret the uninitialized values and delete the
** wrong pages from the database.
*/
if( pBt->autoVacuum && rc==SQLITE_OK ){
u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap, &rc);
if( rc ){
releasePage(pOvfl);
}
}
#endif
if( rc ){
releasePage(pToRelease);
return rc;
}
/* If pToRelease is not zero than pPrior points into the data area
** of pToRelease. Make sure pToRelease is still writeable. */
assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
/* If pPrior is part of the data area of pPage, then make sure pPage
** is still writeable */
assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
put4byte(pPrior, pgnoOvfl);
releasePage(pToRelease);
pToRelease = pOvfl;
pPrior = pOvfl->aData;
put4byte(pPrior, 0);
pPayload = &pOvfl->aData[4];
spaceLeft = pBt->usableSize - 4;
}
}
releasePage(pToRelease);
return SQLITE_OK;
}
/*
** Remove the i-th cell from pPage. This routine effects pPage only.
** The cell content is not freed or deallocated. It is assumed that
** the cell content has been copied someplace else. This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
*/
static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
u32 pc; /* Offset to cell content of cell being deleted */
u8 *data; /* pPage->aData */
u8 *ptr; /* Used to move bytes around within data[] */
int rc; /* The return code */
int hdr; /* Beginning of the header. 0 most pages. 100 page 1 */
if( *pRC ) return;
assert( idx>=0 && idx<pPage->nCell );
assert( CORRUPT_DB || sz==cellSize(pPage, idx) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->nFree>=0 );
data = pPage->aData;
ptr = &pPage->aCellIdx[2*idx];
pc = get2byte(ptr);
hdr = pPage->hdrOffset;
testcase( pc==get2byte(&data[hdr+5]) );
testcase( pc+sz==pPage->pBt->usableSize );
if( pc+sz > pPage->pBt->usableSize ){
*pRC = SQLITE_CORRUPT_BKPT;
return;
}
rc = freeSpace(pPage, pc, sz);
if( rc ){
*pRC = rc;
return;
}
pPage->nCell--;
if( pPage->nCell==0 ){
memset(&data[hdr+1], 0, 4);
data[hdr+7] = 0;
put2byte(&data[hdr+5], pPage->pBt->usableSize);
pPage->nFree = pPage->pBt->usableSize - pPage->hdrOffset
- pPage->childPtrSize - 8;
}else{
memmove(ptr, ptr+2, 2*(pPage->nCell - idx));
put2byte(&data[hdr+3], pPage->nCell);
pPage->nFree += 2;
}
}
/*
** Insert a new cell on pPage at cell index "i". pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there. If it
** will not fit, then make a copy of the cell content into pTemp if
** pTemp is not null. Regardless of pTemp, allocate a new entry
** in pPage->apOvfl[] and make it point to the cell content (either
** in pTemp or the original pCell) and also record its index.
** Allocating a new entry in pPage->aCell[] implies that
** pPage->nOverflow is incremented.
**
** *pRC must be SQLITE_OK when this routine is called.
*/
static void insertCell(
MemPage *pPage, /* Page into which we are copying */
int i, /* New cell becomes the i-th cell of the page */
u8 *pCell, /* Content of the new cell */
int sz, /* Bytes of content in pCell */
u8 *pTemp, /* Temp storage space for pCell, if needed */
Pgno iChild, /* If non-zero, replace first 4 bytes with this value */
int *pRC /* Read and write return code from here */
){
int idx = 0; /* Where to write new cell content in data[] */
int j; /* Loop counter */
u8 *data; /* The content of the whole page */
u8 *pIns; /* The point in pPage->aCellIdx[] where no cell inserted */
assert( *pRC==SQLITE_OK );
assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
assert( MX_CELL(pPage->pBt)<=10921 );
assert( pPage->nCell<=MX_CELL(pPage->pBt) || CORRUPT_DB );
assert( pPage->nOverflow<=ArraySize(pPage->apOvfl) );
assert( ArraySize(pPage->apOvfl)==ArraySize(pPage->aiOvfl) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( sz==pPage->xCellSize(pPage, pCell) || CORRUPT_DB );
assert( pPage->nFree>=0 );
if( pPage->nOverflow || sz+2>pPage->nFree ){
if( pTemp ){
memcpy(pTemp, pCell, sz);
pCell = pTemp;
}
if( iChild ){
put4byte(pCell, iChild);
}
j = pPage->nOverflow++;
/* Comparison against ArraySize-1 since we hold back one extra slot
** as a contingency. In other words, never need more than 3 overflow
** slots but 4 are allocated, just to be safe. */
assert( j < ArraySize(pPage->apOvfl)-1 );
pPage->apOvfl[j] = pCell;
pPage->aiOvfl[j] = (u16)i;
/* When multiple overflows occur, they are always sequential and in
** sorted order. This invariants arise because multiple overflows can
** only occur when inserting divider cells into the parent page during
** balancing, and the dividers are adjacent and sorted.
*/
assert( j==0 || pPage->aiOvfl[j-1]<(u16)i ); /* Overflows in sorted order */
assert( j==0 || i==pPage->aiOvfl[j-1]+1 ); /* Overflows are sequential */
}else{
int rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
*pRC = rc;
return;
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
data = pPage->aData;
assert( &data[pPage->cellOffset]==pPage->aCellIdx );
rc = allocateSpace(pPage, sz, &idx);
if( rc ){ *pRC = rc; return; }
/* The allocateSpace() routine guarantees the following properties
** if it returns successfully */
assert( idx >= 0 );
assert( idx >= pPage->cellOffset+2*pPage->nCell+2 || CORRUPT_DB );
assert( idx+sz <= (int)pPage->pBt->usableSize );
pPage->nFree -= (u16)(2 + sz);
if( iChild ){
/* In a corrupt database where an entry in the cell index section of
** a btree page has a value of 3 or less, the pCell value might point
** as many as 4 bytes in front of the start of the aData buffer for
** the source page. Make sure this does not cause problems by not
** reading the first 4 bytes */
memcpy(&data[idx+4], pCell+4, sz-4);
put4byte(&data[idx], iChild);
}else{
memcpy(&data[idx], pCell, sz);
}
pIns = pPage->aCellIdx + i*2;
memmove(pIns+2, pIns, 2*(pPage->nCell - i));
put2byte(pIns, idx);
pPage->nCell++;
/* increment the cell count */
if( (++data[pPage->hdrOffset+4])==0 ) data[pPage->hdrOffset+3]++;
assert( get2byte(&data[pPage->hdrOffset+3])==pPage->nCell || CORRUPT_DB );
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pPage->pBt->autoVacuum ){
/* The cell may contain a pointer to an overflow page. If so, write
** the entry for the overflow page into the pointer map.
*/
ptrmapPutOvflPtr(pPage, pPage, pCell, pRC);
}
#endif
}
}
/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation. NN is the number of neighbors on either side
** of the page that participate in the balancing operation. NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
** The minimum value of NN is 1 (of course). Increasing NN above 1
** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
** in exchange for a larger degradation in INSERT and UPDATE performance.
** The value of NN appears to give the best results overall.
**
** (Later:) The description above makes it seem as if these values are
** tunable - as if you could change them and recompile and it would all work.
** But that is unlikely. NB has been 3 since the inception of SQLite and
** we have never tested any other value.
*/
#define NN 1 /* Number of neighbors on either side of pPage */
#define NB 3 /* (NN*2+1): Total pages involved in the balance */
/*
** A CellArray object contains a cache of pointers and sizes for a
** consecutive sequence of cells that might be held on multiple pages.
**
** The cells in this array are the divider cell or cells from the pParent
** page plus up to three child pages. There are a total of nCell cells.
**
** pRef is a pointer to one of the pages that contributes cells. This is
** used to access information such as MemPage.intKey and MemPage.pBt->pageSize
** which should be common to all pages that contribute cells to this array.
**
** apCell[] and szCell[] hold, respectively, pointers to the start of each
** cell and the size of each cell. Some of the apCell[] pointers might refer
** to overflow cells. In other words, some apCel[] pointers might not point
** to content area of the pages.
**
** A szCell[] of zero means the size of that cell has not yet been computed.
**
** The cells come from as many as four different pages:
**
** -----------
** | Parent |
** -----------
** / | \
** / | \
** --------- --------- ---------
** |Child-1| |Child-2| |Child-3|
** --------- --------- ---------
**
** The order of cells is in the array is for an index btree is:
**
** 1. All cells from Child-1 in order
** 2. The first divider cell from Parent
** 3. All cells from Child-2 in order
** 4. The second divider cell from Parent
** 5. All cells from Child-3 in order
**
** For a table-btree (with rowids) the items 2 and 4 are empty because
** content exists only in leaves and there are no divider cells.
**
** For an index btree, the apEnd[] array holds pointer to the end of page
** for Child-1, the Parent, Child-2, the Parent (again), and Child-3,
** respectively. The ixNx[] array holds the number of cells contained in
** each of these 5 stages, and all stages to the left. Hence:
**
** ixNx[0] = Number of cells in Child-1.
** ixNx[1] = Number of cells in Child-1 plus 1 for first divider.
** ixNx[2] = Number of cells in Child-1 and Child-2 + 1 for 1st divider.
** ixNx[3] = Number of cells in Child-1 and Child-2 + both divider cells
** ixNx[4] = Total number of cells.
**
** For a table-btree, the concept is similar, except only apEnd[0]..apEnd[2]
** are used and they point to the leaf pages only, and the ixNx value are:
**
** ixNx[0] = Number of cells in Child-1.
** ixNx[1] = Number of cells in Child-1 and Child-2.
** ixNx[2] = Total number of cells.
**
** Sometimes when deleting, a child page can have zero cells. In those
** cases, ixNx[] entries with higher indexes, and the corresponding apEnd[]
** entries, shift down. The end result is that each ixNx[] entry should
** be larger than the previous
*/
typedef struct CellArray CellArray;
struct CellArray {
int nCell; /* Number of cells in apCell[] */
MemPage *pRef; /* Reference page */
u8 **apCell; /* All cells begin balanced */
u16 *szCell; /* Local size of all cells in apCell[] */
u8 *apEnd[NB*2]; /* MemPage.aDataEnd values */
int ixNx[NB*2]; /* Index of at which we move to the next apEnd[] */
};
/*
** Make sure the cell sizes at idx, idx+1, ..., idx+N-1 have been
** computed.
*/
static void populateCellCache(CellArray *p, int idx, int N){
assert( idx>=0 && idx+N<=p->nCell );
while( N>0 ){
assert( p->apCell[idx]!=0 );
if( p->szCell[idx]==0 ){
p->szCell[idx] = p->pRef->xCellSize(p->pRef, p->apCell[idx]);
}else{
assert( CORRUPT_DB ||
p->szCell[idx]==p->pRef->xCellSize(p->pRef, p->apCell[idx]) );
}
idx++;
N--;
}
}
/*
** Return the size of the Nth element of the cell array
*/
static SQLITE_NOINLINE u16 computeCellSize(CellArray *p, int N){
assert( N>=0 && N<p->nCell );
assert( p->szCell[N]==0 );
p->szCell[N] = p->pRef->xCellSize(p->pRef, p->apCell[N]);
return p->szCell[N];
}
static u16 cachedCellSize(CellArray *p, int N){
assert( N>=0 && N<p->nCell );
if( p->szCell[N] ) return p->szCell[N];
return computeCellSize(p, N);
}
/*
** Array apCell[] contains pointers to nCell b-tree page cells. The
** szCell[] array contains the size in bytes of each cell. This function
** replaces the current contents of page pPg with the contents of the cell
** array.
**
** Some of the cells in apCell[] may currently be stored in pPg. This
** function works around problems caused by this by making a copy of any
** such cells before overwriting the page data.
**
** The MemPage.nFree field is invalidated by this function. It is the
** responsibility of the caller to set it correctly.
*/
static int rebuildPage(
CellArray *pCArray, /* Content to be added to page pPg */
int iFirst, /* First cell in pCArray to use */
int nCell, /* Final number of cells on page */
MemPage *pPg /* The page to be reconstructed */
){
const int hdr = pPg->hdrOffset; /* Offset of header on pPg */
u8 * const aData = pPg->aData; /* Pointer to data for pPg */
const int usableSize = pPg->pBt->usableSize;
u8 * const pEnd = &aData[usableSize];
int i = iFirst; /* Which cell to copy from pCArray*/
u32 j; /* Start of cell content area */
int iEnd = i+nCell; /* Loop terminator */
u8 *pCellptr = pPg->aCellIdx;
u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
u8 *pData;
int k; /* Current slot in pCArray->apEnd[] */
u8 *pSrcEnd; /* Current pCArray->apEnd[k] value */
assert( i<iEnd );
j = get2byte(&aData[hdr+5]);
if( NEVER(j>(u32)usableSize) ){ j = 0; }
memcpy(&pTmp[j], &aData[j], usableSize - j);
for(k=0; pCArray->ixNx[k]<=i && ALWAYS(k<NB*2); k++){}
pSrcEnd = pCArray->apEnd[k];
pData = pEnd;
while( 1/*exit by break*/ ){
u8 *pCell = pCArray->apCell[i];
u16 sz = pCArray->szCell[i];
assert( sz>0 );
if( SQLITE_WITHIN(pCell,aData,pEnd) ){
if( ((uptr)(pCell+sz))>(uptr)pEnd ) return SQLITE_CORRUPT_BKPT;
pCell = &pTmp[pCell - aData];
}else if( (uptr)(pCell+sz)>(uptr)pSrcEnd
&& (uptr)(pCell)<(uptr)pSrcEnd
){
return SQLITE_CORRUPT_BKPT;
}
pData -= sz;
put2byte(pCellptr, (pData - aData));
pCellptr += 2;
if( pData < pCellptr ) return SQLITE_CORRUPT_BKPT;
memcpy(pData, pCell, sz);
assert( sz==pPg->xCellSize(pPg, pCell) || CORRUPT_DB );
testcase( sz!=pPg->xCellSize(pPg,pCell) )
i++;
if( i>=iEnd ) break;
if( pCArray->ixNx[k]<=i ){
k++;
pSrcEnd = pCArray->apEnd[k];
}
}
/* The pPg->nFree field is now set incorrectly. The caller will fix it. */
pPg->nCell = nCell;
pPg->nOverflow = 0;
put2byte(&aData[hdr+1], 0);
put2byte(&aData[hdr+3], pPg->nCell);
put2byte(&aData[hdr+5], pData - aData);
aData[hdr+7] = 0x00;
return SQLITE_OK;
}
/*
** The pCArray objects contains pointers to b-tree cells and the cell sizes.
** This function attempts to add the cells stored in the array to page pPg.
** If it cannot (because the page needs to be defragmented before the cells
** will fit), non-zero is returned. Otherwise, if the cells are added
** successfully, zero is returned.
**
** Argument pCellptr points to the first entry in the cell-pointer array
** (part of page pPg) to populate. After cell apCell[0] is written to the
** page body, a 16-bit offset is written to pCellptr. And so on, for each
** cell in the array. It is the responsibility of the caller to ensure
** that it is safe to overwrite this part of the cell-pointer array.
**
** When this function is called, *ppData points to the start of the
** content area on page pPg. If the size of the content area is extended,
** *ppData is updated to point to the new start of the content area
** before returning.
**
** Finally, argument pBegin points to the byte immediately following the
** end of the space required by this page for the cell-pointer area (for
** all cells - not just those inserted by the current call). If the content
** area must be extended to before this point in order to accomodate all
** cells in apCell[], then the cells do not fit and non-zero is returned.
*/
static int pageInsertArray(
MemPage *pPg, /* Page to add cells to */
u8 *pBegin, /* End of cell-pointer array */
u8 **ppData, /* IN/OUT: Page content-area pointer */
u8 *pCellptr, /* Pointer to cell-pointer area */
int iFirst, /* Index of first cell to add */
int nCell, /* Number of cells to add to pPg */
CellArray *pCArray /* Array of cells */
){
int i = iFirst; /* Loop counter - cell index to insert */
u8 *aData = pPg->aData; /* Complete page */
u8 *pData = *ppData; /* Content area. A subset of aData[] */
int iEnd = iFirst + nCell; /* End of loop. One past last cell to ins */
int k; /* Current slot in pCArray->apEnd[] */
u8 *pEnd; /* Maximum extent of cell data */
assert( CORRUPT_DB || pPg->hdrOffset==0 ); /* Never called on page 1 */
if( iEnd<=iFirst ) return 0;
for(k=0; pCArray->ixNx[k]<=i && ALWAYS(k<NB*2); k++){}
pEnd = pCArray->apEnd[k];
while( 1 /*Exit by break*/ ){
int sz, rc;
u8 *pSlot;
assert( pCArray->szCell[i]!=0 );
sz = pCArray->szCell[i];
if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
if( (pData - pBegin)<sz ) return 1;
pData -= sz;
pSlot = pData;
}
/* pSlot and pCArray->apCell[i] will never overlap on a well-formed
** database. But they might for a corrupt database. Hence use memmove()
** since memcpy() sends SIGABORT with overlapping buffers on OpenBSD */
assert( (pSlot+sz)<=pCArray->apCell[i]
|| pSlot>=(pCArray->apCell[i]+sz)
|| CORRUPT_DB );
if( (uptr)(pCArray->apCell[i]+sz)>(uptr)pEnd
&& (uptr)(pCArray->apCell[i])<(uptr)pEnd
){
assert( CORRUPT_DB );
(void)SQLITE_CORRUPT_BKPT;
return 1;
}
memmove(pSlot, pCArray->apCell[i], sz);
put2byte(pCellptr, (pSlot - aData));
pCellptr += 2;
i++;
if( i>=iEnd ) break;
if( pCArray->ixNx[k]<=i ){
k++;
pEnd = pCArray->apEnd[k];
}
}
*ppData = pData;
return 0;
}
/*
** The pCArray object contains pointers to b-tree cells and their sizes.
**
** This function adds the space associated with each cell in the array
** that is currently stored within the body of pPg to the pPg free-list.
** The cell-pointers and other fields of the page are not updated.
**
** This function returns the total number of cells added to the free-list.
*/
static int pageFreeArray(
MemPage *pPg, /* Page to edit */
int iFirst, /* First cell to delete */
int nCell, /* Cells to delete */
CellArray *pCArray /* Array of cells */
){
u8 * const aData = pPg->aData;
u8 * const pEnd = &aData[pPg->pBt->usableSize];
u8 * const pStart = &aData[pPg->hdrOffset + 8 + pPg->childPtrSize];
int nRet = 0;
int i;
int iEnd = iFirst + nCell;
u8 *pFree = 0;
int szFree = 0;
for(i=iFirst; i<iEnd; i++){
u8 *pCell = pCArray->apCell[i];
if( SQLITE_WITHIN(pCell, pStart, pEnd) ){
int sz;
/* No need to use cachedCellSize() here. The sizes of all cells that
** are to be freed have already been computing while deciding which
** cells need freeing */
sz = pCArray->szCell[i]; assert( sz>0 );
if( pFree!=(pCell + sz) ){
if( pFree ){
assert( pFree>aData && (pFree - aData)<65536 );
freeSpace(pPg, (u16)(pFree - aData), szFree);
}
pFree = pCell;
szFree = sz;
if( pFree+sz>pEnd ) return 0;
}else{
pFree = pCell;
szFree += sz;
}
nRet++;
}
}
if( pFree ){
assert( pFree>aData && (pFree - aData)<65536 );
freeSpace(pPg, (u16)(pFree - aData), szFree);
}
return nRet;
}
/*
** pCArray contains pointers to and sizes of all cells in the page being
** balanced. The current page, pPg, has pPg->nCell cells starting with
** pCArray->apCell[iOld]. After balancing, this page should hold nNew cells
** starting at apCell[iNew].
**
** This routine makes the necessary adjustments to pPg so that it contains
** the correct cells after being balanced.
**
** The pPg->nFree field is invalid when this function returns. It is the
** responsibility of the caller to set it correctly.
*/
static int editPage(
MemPage *pPg, /* Edit this page */
int iOld, /* Index of first cell currently on page */
int iNew, /* Index of new first cell on page */
int nNew, /* Final number of cells on page */
CellArray *pCArray /* Array of cells and sizes */
){
u8 * const aData = pPg->aData;
const int hdr = pPg->hdrOffset;
u8 *pBegin = &pPg->aCellIdx[nNew * 2];
int nCell = pPg->nCell; /* Cells stored on pPg */
u8 *pData;
u8 *pCellptr;
int i;
int iOldEnd = iOld + pPg->nCell + pPg->nOverflow;
int iNewEnd = iNew + nNew;
#ifdef SQLITE_DEBUG
u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
memcpy(pTmp, aData, pPg->pBt->usableSize);
#endif
/* Remove cells from the start and end of the page */
assert( nCell>=0 );
if( iOld<iNew ){
int nShift = pageFreeArray(pPg, iOld, iNew-iOld, pCArray);
if( NEVER(nShift>nCell) ) return SQLITE_CORRUPT_BKPT;
memmove(pPg->aCellIdx, &pPg->aCellIdx[nShift*2], nCell*2);
nCell -= nShift;
}
if( iNewEnd < iOldEnd ){
int nTail = pageFreeArray(pPg, iNewEnd, iOldEnd - iNewEnd, pCArray);
assert( nCell>=nTail );
nCell -= nTail;
}
pData = &aData[get2byteNotZero(&aData[hdr+5])];
if( pData<pBegin ) goto editpage_fail;
/* Add cells to the start of the page */
if( iNew<iOld ){
int nAdd = MIN(nNew,iOld-iNew);
assert( (iOld-iNew)<nNew || nCell==0 || CORRUPT_DB );
assert( nAdd>=0 );
pCellptr = pPg->aCellIdx;
memmove(&pCellptr[nAdd*2], pCellptr, nCell*2);
if( pageInsertArray(
pPg, pBegin, &pData, pCellptr,
iNew, nAdd, pCArray
) ) goto editpage_fail;
nCell += nAdd;
}
/* Add any overflow cells */
for(i=0; i<pPg->nOverflow; i++){
int iCell = (iOld + pPg->aiOvfl[i]) - iNew;
if( iCell>=0 && iCell<nNew ){
pCellptr = &pPg->aCellIdx[iCell * 2];
if( nCell>iCell ){
memmove(&pCellptr[2], pCellptr, (nCell - iCell) * 2);
}
nCell++;
cachedCellSize(pCArray, iCell+iNew);
if( pageInsertArray(
pPg, pBegin, &pData, pCellptr,
iCell+iNew, 1, pCArray
) ) goto editpage_fail;
}
}
/* Append cells to the end of the page */
assert( nCell>=0 );
pCellptr = &pPg->aCellIdx[nCell*2];
if( pageInsertArray(
pPg, pBegin, &pData, pCellptr,
iNew+nCell, nNew-nCell, pCArray
) ) goto editpage_fail;
pPg->nCell = nNew;
pPg->nOverflow = 0;
put2byte(&aData[hdr+3], pPg->nCell);
put2byte(&aData[hdr+5], pData - aData);
#ifdef SQLITE_DEBUG
for(i=0; i<nNew && !CORRUPT_DB; i++){
u8 *pCell = pCArray->apCell[i+iNew];
int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
if( SQLITE_WITHIN(pCell, aData, &aData[pPg->pBt->usableSize]) ){
pCell = &pTmp[pCell - aData];
}
assert( 0==memcmp(pCell, &aData[iOff],
pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
}
#endif
return SQLITE_OK;
editpage_fail:
/* Unable to edit this page. Rebuild it from scratch instead. */
populateCellCache(pCArray, iNew, nNew);
return rebuildPage(pCArray, iNew, nNew, pPg);
}
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** This version of balance() handles the common special case where
** a new entry is being inserted on the extreme right-end of the
** tree, in other words, when the new entry will become the largest
** entry in the tree.
**
** Instead of trying to balance the 3 right-most leaf pages, just add
** a new page to the right-hand side and put the one new entry in
** that page. This leaves the right side of the tree somewhat
** unbalanced. But odds are that we will be inserting new entries
** at the end soon afterwards so the nearly empty page will quickly
** fill up. On average.
**
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent. pPage must have a single overflow entry
** which is also the right-most entry on the page.
**
** The pSpace buffer is used to store a temporary copy of the divider
** cell that will be inserted into pParent. Such a cell consists of a 4
** byte page number followed by a variable length integer. In other
** words, at most 13 bytes. Hence the pSpace buffer must be at
** least 13 bytes in size.
*/
static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
BtShared *const pBt = pPage->pBt; /* B-Tree Database */
MemPage *pNew; /* Newly allocated page */
int rc; /* Return Code */
Pgno pgnoNew; /* Page number of pNew */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
assert( pPage->nOverflow==1 );
if( pPage->nCell==0 ) return SQLITE_CORRUPT_BKPT; /* dbfuzz001.test */
assert( pPage->nFree>=0 );
assert( pParent->nFree>=0 );
/* Allocate a new page. This page will become the right-sibling of
** pPage. Make the parent page writable, so that the new divider cell
** may be inserted. If both these operations are successful, proceed.
*/
rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
if( rc==SQLITE_OK ){
u8 *pOut = &pSpace[4];
u8 *pCell = pPage->apOvfl[0];
u16 szCell = pPage->xCellSize(pPage, pCell);
u8 *pStop;
CellArray b;
assert( sqlite3PagerIswriteable(pNew->pDbPage) );
assert( CORRUPT_DB || pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
b.nCell = 1;
b.pRef = pPage;
b.apCell = &pCell;
b.szCell = &szCell;
b.apEnd[0] = pPage->aDataEnd;
b.ixNx[0] = 2;
rc = rebuildPage(&b, 0, 1, pNew);
if( NEVER(rc) ){
releasePage(pNew);
return rc;
}
pNew->nFree = pBt->usableSize - pNew->cellOffset - 2 - szCell;
/* If this is an auto-vacuum database, update the pointer map
** with entries for the new page, and any pointer from the
** cell on the page to an overflow page. If either of these
** operations fails, the return code is set, but the contents
** of the parent page are still manipulated by thh code below.
** That is Ok, at this point the parent page is guaranteed to
** be marked as dirty. Returning an error code will cause a
** rollback, undoing any changes made to the parent page.
*/
if( ISAUTOVACUUM ){
ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno, &rc);
if( szCell>pNew->minLocal ){
ptrmapPutOvflPtr(pNew, pNew, pCell, &rc);
}
}
/* Create a divider cell to insert into pParent. The divider cell
** consists of a 4-byte page number (the page number of pPage) and
** a variable length key value (which must be the same value as the
** largest key on pPage).
**
** To find the largest key value on pPage, first find the right-most
** cell on pPage. The first two fields of this cell are the
** record-length (a variable length integer at most 32-bits in size)
** and the key value (a variable length integer, may have any value).
** The first of the while(...) loops below skips over the record-length
** field. The second while(...) loop copies the key value from the
** cell on pPage into the pSpace buffer.
*/
pCell = findCell(pPage, pPage->nCell-1);
pStop = &pCell[9];
while( (*(pCell++)&0x80) && pCell<pStop );
pStop = &pCell[9];
while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );
/* Insert the new divider cell into pParent. */
if( rc==SQLITE_OK ){
insertCell(pParent, pParent->nCell, pSpace, (int)(pOut-pSpace),
0, pPage->pgno, &rc);
}
/* Set the right-child pointer of pParent to point to the new page. */
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
/* Release the reference to the new page. */
releasePage(pNew);
}
return rc;
}
#endif /* SQLITE_OMIT_QUICKBALANCE */
#if 0
/*
** This function does not contribute anything to the operation of SQLite.
** it is sometimes activated temporarily while debugging code responsible
** for setting pointer-map entries.
*/
static int ptrmapCheckPages(MemPage **apPage, int nPage){
int i, j;
for(i=0; i<nPage; i++){
Pgno n;
u8 e;
MemPage *pPage = apPage[i];
BtShared *pBt = pPage->pBt;
assert( pPage->isInit );
for(j=0; j<pPage->nCell; j++){
CellInfo info;
u8 *z;
z = findCell(pPage, j);
pPage->xParseCell(pPage, z, &info);
if( info.nLocal<info.nPayload ){
Pgno ovfl = get4byte(&z[info.nSize-4]);
ptrmapGet(pBt, ovfl, &e, &n);
assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
}
if( !pPage->leaf ){
Pgno child = get4byte(z);
ptrmapGet(pBt, child, &e, &n);
assert( n==pPage->pgno && e==PTRMAP_BTREE );
}
}
if( !pPage->leaf ){
Pgno child = get4byte(&pPage->aData[pPage->hdrOffset+8]);
ptrmapGet(pBt, child, &e, &n);
assert( n==pPage->pgno && e==PTRMAP_BTREE );
}
}
return 1;
}
#endif
/*
** This function is used to copy the contents of the b-tree node stored
** on page pFrom to page pTo. If page pFrom was not a leaf page, then
** the pointer-map entries for each child page are updated so that the
** parent page stored in the pointer map is page pTo. If pFrom contained
** any cells with overflow page pointers, then the corresponding pointer
** map entries are also updated so that the parent page is page pTo.
**
** If pFrom is currently carrying any overflow cells (entries in the
** MemPage.apOvfl[] array), they are not copied to pTo.
**
** Before returning, page pTo is reinitialized using btreeInitPage().
**
** The performance of this function is not critical. It is only used by
** the balance_shallower() and balance_deeper() procedures, neither of
** which are called often under normal circumstances.
*/
static void copyNodeContent(MemPage *pFrom, MemPage *pTo, int *pRC){
if( (*pRC)==SQLITE_OK ){
BtShared * const pBt = pFrom->pBt;
u8 * const aFrom = pFrom->aData;
u8 * const aTo = pTo->aData;
int const iFromHdr = pFrom->hdrOffset;
int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
int rc;
int iData;
assert( pFrom->isInit );
assert( pFrom->nFree>=iToHdr );
assert( get2byte(&aFrom[iFromHdr+5]) <= (int)pBt->usableSize );
/* Copy the b-tree node content from page pFrom to page pTo. */
iData = get2byte(&aFrom[iFromHdr+5]);
memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
/* Reinitialize page pTo so that the contents of the MemPage structure
** match the new data. The initialization of pTo can actually fail under
** fairly obscure circumstances, even though it is a copy of initialized
** page pFrom.
*/
pTo->isInit = 0;
rc = btreeInitPage(pTo);
if( rc==SQLITE_OK ) rc = btreeComputeFreeSpace(pTo);
if( rc!=SQLITE_OK ){
*pRC = rc;
return;
}
/* If this is an auto-vacuum database, update the pointer-map entries
** for any b-tree or overflow pages that pTo now contains the pointers to.
*/
if( ISAUTOVACUUM ){
*pRC = setChildPtrmaps(pTo);
}
}
}
/*
** This routine redistributes cells on the iParentIdx'th child of pParent
** (hereafter "the page") and up to 2 siblings so that all pages have about the
** same amount of free space. Usually a single sibling on either side of the
** page are used in the balancing, though both siblings might come from one
** side if the page is the first or last child of its parent. If the page
** has fewer than 2 siblings (something which can only happen if the page
** is a root page or a child of a root page) then all available siblings
** participate in the balancing.
**
** The number of siblings of the page might be increased or decreased by
** one or two in an effort to keep pages nearly full but not over full.
**
** Note that when this routine is called, some of the cells on the page
** might not actually be stored in MemPage.aData[]. This can happen
** if the page is overfull. This routine ensures that all cells allocated
** to the page and its siblings fit into MemPage.aData[] before returning.
**
** In the course of balancing the page and its siblings, cells may be
** inserted into or removed from the parent page (pParent). Doing so
** may cause the parent page to become overfull or underfull. If this
** happens, it is the responsibility of the caller to invoke the correct
** balancing routine to fix this problem (see the balance() routine).
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
**
** The third argument to this function, aOvflSpace, is a pointer to a
** buffer big enough to hold one page. If while inserting cells into the parent
** page (pParent) the parent page becomes overfull, this buffer is
** used to store the parent's overflow cells. Because this function inserts
** a maximum of four divider cells into the parent page, and the maximum
** size of a cell stored within an internal node is always less than 1/4
** of the page-size, the aOvflSpace[] buffer is guaranteed to be large
** enough for all overflow cells.
**
** If aOvflSpace is set to a null pointer, this function returns
** SQLITE_NOMEM.
*/
static int balance_nonroot(
MemPage *pParent, /* Parent page of siblings being balanced */
int iParentIdx, /* Index of "the page" in pParent */
u8 *aOvflSpace, /* page-size bytes of space for parent ovfl */
int isRoot, /* True if pParent is a root-page */
int bBulk /* True if this call is part of a bulk load */
){
BtShared *pBt; /* The whole database */
int nMaxCells = 0; /* Allocated size of apCell, szCell, aFrom. */
int nNew = 0; /* Number of pages in apNew[] */
int nOld; /* Number of pages in apOld[] */
int i, j, k; /* Loop counters */
int nxDiv; /* Next divider slot in pParent->aCell[] */
int rc = SQLITE_OK; /* The return code */
u16 leafCorrection; /* 4 if pPage is a leaf. 0 if not */
int leafData; /* True if pPage is a leaf of a LEAFDATA tree */
int usableSpace; /* Bytes in pPage beyond the header */
int pageFlags; /* Value of pPage->aData[0] */
int iSpace1 = 0; /* First unused byte of aSpace1[] */
int iOvflSpace = 0; /* First unused byte of aOvflSpace[] */
int szScratch; /* Size of scratch memory requested */
MemPage *apOld[NB]; /* pPage and up to two siblings */
MemPage *apNew[NB+2]; /* pPage and up to NB siblings after balancing */
u8 *pRight; /* Location in parent of right-sibling pointer */
u8 *apDiv[NB-1]; /* Divider cells in pParent */
int cntNew[NB+2]; /* Index in b.paCell[] of cell after i-th page */
int cntOld[NB+2]; /* Old index in b.apCell[] */
int szNew[NB+2]; /* Combined size of cells placed on i-th page */
u8 *aSpace1; /* Space for copies of dividers cells */
Pgno pgno; /* Temp var to store a page number in */
u8 abDone[NB+2]; /* True after i'th new page is populated */
Pgno aPgno[NB+2]; /* Page numbers of new pages before shuffling */
Pgno aPgOrder[NB+2]; /* Copy of aPgno[] used for sorting pages */
u16 aPgFlags[NB+2]; /* flags field of new pages before shuffling */
CellArray b; /* Parsed information on cells being balanced */
memset(abDone, 0, sizeof(abDone));
b.nCell = 0;
b.apCell = 0;
pBt = pParent->pBt;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
/* At this point pParent may have at most one overflow cell. And if
** this overflow cell is present, it must be the cell with
** index iParentIdx. This scenario comes about when this function
** is called (indirectly) from sqlite3BtreeDelete().
*/
assert( pParent->nOverflow==0 || pParent->nOverflow==1 );
assert( pParent->nOverflow==0 || pParent->aiOvfl[0]==iParentIdx );
if( !aOvflSpace ){
return SQLITE_NOMEM_BKPT;
}
assert( pParent->nFree>=0 );
/* Find the sibling pages to balance. Also locate the cells in pParent
** that divide the siblings. An attempt is made to find NN siblings on
** either side of pPage. More siblings are taken from one side, however,
** if there are fewer than NN siblings on the other side. If pParent
** has NB or fewer children then all children of pParent are taken.
**
** This loop also drops the divider cells from the parent page. This
** way, the remainder of the function does not have to deal with any
** overflow cells in the parent page, since if any existed they will
** have already been removed.
*/
i = pParent->nOverflow + pParent->nCell;
if( i<2 ){
nxDiv = 0;
}else{
assert( bBulk==0 || bBulk==1 );
if( iParentIdx==0 ){
nxDiv = 0;
}else if( iParentIdx==i ){
nxDiv = i-2+bBulk;
}else{
nxDiv = iParentIdx-1;
}
i = 2-bBulk;
}
nOld = i+1;
if( (i+nxDiv-pParent->nOverflow)==pParent->nCell ){
pRight = &pParent->aData[pParent->hdrOffset+8];
}else{
pRight = findCell(pParent, i+nxDiv-pParent->nOverflow);
}
pgno = get4byte(pRight);
while( 1 ){
if( rc==SQLITE_OK ){
rc = getAndInitPage(pBt, pgno, &apOld[i], 0, 0);
}
if( rc ){
memset(apOld, 0, (i+1)*sizeof(MemPage*));
goto balance_cleanup;
}
if( apOld[i]->nFree<0 ){
rc = btreeComputeFreeSpace(apOld[i]);
if( rc ){
memset(apOld, 0, (i)*sizeof(MemPage*));
goto balance_cleanup;
}
}
if( (i--)==0 ) break;
if( pParent->nOverflow && i+nxDiv==pParent->aiOvfl[0] ){
apDiv[i] = pParent->apOvfl[0];
pgno = get4byte(apDiv[i]);
szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
pParent->nOverflow = 0;
}else{
apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
pgno = get4byte(apDiv[i]);
szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
/* Drop the cell from the parent page. apDiv[i] still points to
** the cell within the parent, even though it has been dropped.
** This is safe because dropping a cell only overwrites the first
** four bytes of it, and this function does not need the first
** four bytes of the divider cell. So the pointer is safe to use
** later on.
**
** But not if we are in secure-delete mode. In secure-delete mode,
** the dropCell() routine will overwrite the entire cell with zeroes.
** In this case, temporarily copy the cell into the aOvflSpace[]
** buffer. It will be copied out again as soon as the aSpace[] buffer
** is allocated. */
if( pBt->btsFlags & BTS_FAST_SECURE ){
int iOff;
/* If the following if() condition is not true, the db is corrupted.
** The call to dropCell() below will detect this. */
iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
if( (iOff+szNew[i])<=(int)pBt->usableSize ){
memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
}
}
dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
}
}
/* Make nMaxCells a multiple of 4 in order to preserve 8-byte
** alignment */
nMaxCells = nOld*(MX_CELL(pBt) + ArraySize(pParent->apOvfl));
nMaxCells = (nMaxCells + 3)&~3;
/*
** Allocate space for memory structures
*/
szScratch =
nMaxCells*sizeof(u8*) /* b.apCell */
+ nMaxCells*sizeof(u16) /* b.szCell */
+ pBt->pageSize; /* aSpace1 */
assert( szScratch<=7*(int)pBt->pageSize );
b.apCell = sqlite3StackAllocRaw(0, szScratch );
if( b.apCell==0 ){
rc = SQLITE_NOMEM_BKPT;
goto balance_cleanup;
}
b.szCell = (u16*)&b.apCell[nMaxCells];
aSpace1 = (u8*)&b.szCell[nMaxCells];
assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );
/*
** Load pointers to all cells on sibling pages and the divider cells
** into the local b.apCell[] array. Make copies of the divider cells
** into space obtained from aSpace1[]. The divider cells have already
** been removed from pParent.
**
** If the siblings are on leaf pages, then the child pointers of the
** divider cells are stripped from the cells before they are copied
** into aSpace1[]. In this way, all cells in b.apCell[] are without
** child pointers. If siblings are not leaves, then all cell in
** b.apCell[] include child pointers. Either way, all cells in b.apCell[]
** are alike.
**
** leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf.
** leafData: 1 if pPage holds key+data and pParent holds only keys.
*/
b.pRef = apOld[0];
leafCorrection = b.pRef->leaf*4;
leafData = b.pRef->intKeyLeaf;
for(i=0; i<nOld; i++){
MemPage *pOld = apOld[i];
int limit = pOld->nCell;
u8 *aData = pOld->aData;
u16 maskPage = pOld->maskPage;
u8 *piCell = aData + pOld->cellOffset;
u8 *piEnd;
VVA_ONLY( int nCellAtStart = b.nCell; )
/* Verify that all sibling pages are of the same "type" (table-leaf,
** table-interior, index-leaf, or index-interior).
*/
if( pOld->aData[0]!=apOld[0]->aData[0] ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
/* Load b.apCell[] with pointers to all cells in pOld. If pOld
** contains overflow cells, include them in the b.apCell[] array
** in the correct spot.
**
** Note that when there are multiple overflow cells, it is always the
** case that they are sequential and adjacent. This invariant arises
** because multiple overflows can only occurs when inserting divider
** cells into a parent on a prior balance, and divider cells are always
** adjacent and are inserted in order. There is an assert() tagged
** with "NOTE 1" in the overflow cell insertion loop to prove this
** invariant.
**
** This must be done in advance. Once the balance starts, the cell
** offset section of the btree page will be overwritten and we will no
** long be able to find the cells if a pointer to each cell is not saved
** first.
*/
memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*(limit+pOld->nOverflow));
if( pOld->nOverflow>0 ){
if( NEVER(limit<pOld->aiOvfl[0]) ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
limit = pOld->aiOvfl[0];
for(j=0; j<limit; j++){
b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
piCell += 2;
b.nCell++;
}
for(k=0; k<pOld->nOverflow; k++){
assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
b.apCell[b.nCell] = pOld->apOvfl[k];
b.nCell++;
}
}
piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
while( piCell<piEnd ){
assert( b.nCell<nMaxCells );
b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
piCell += 2;
b.nCell++;
}
assert( (b.nCell-nCellAtStart)==(pOld->nCell+pOld->nOverflow) );
cntOld[i] = b.nCell;
if( i<nOld-1 && !leafData){
u16 sz = (u16)szNew[i];
u8 *pTemp;
assert( b.nCell<nMaxCells );
b.szCell[b.nCell] = sz;
pTemp = &aSpace1[iSpace1];
iSpace1 += sz;
assert( sz<=pBt->maxLocal+23 );
assert( iSpace1 <= (int)pBt->pageSize );
memcpy(pTemp, apDiv[i], sz);
b.apCell[b.nCell] = pTemp+leafCorrection;
assert( leafCorrection==0 || leafCorrection==4 );
b.szCell[b.nCell] = b.szCell[b.nCell] - leafCorrection;
if( !pOld->leaf ){
assert( leafCorrection==0 );
assert( pOld->hdrOffset==0 );
/* The right pointer of the child page pOld becomes the left
** pointer of the divider cell */
memcpy(b.apCell[b.nCell], &pOld->aData[8], 4);
}else{
assert( leafCorrection==4 );
while( b.szCell[b.nCell]<4 ){
/* Do not allow any cells smaller than 4 bytes. If a smaller cell
** does exist, pad it with 0x00 bytes. */
assert( b.szCell[b.nCell]==3 || CORRUPT_DB );
assert( b.apCell[b.nCell]==&aSpace1[iSpace1-3] || CORRUPT_DB );
aSpace1[iSpace1++] = 0x00;
b.szCell[b.nCell]++;
}
}
b.nCell++;
}
}
/*
** Figure out the number of pages needed to hold all b.nCell cells.
** Store this number in "k". Also compute szNew[] which is the total
** size of all cells on the i-th page and cntNew[] which is the index
** in b.apCell[] of the cell that divides page i from page i+1.
** cntNew[k] should equal b.nCell.
**
** Values computed by this block:
**
** k: The total number of sibling pages
** szNew[i]: Spaced used on the i-th sibling page.
** cntNew[i]: Index in b.apCell[] and b.szCell[] for the first cell to
** the right of the i-th sibling page.
** usableSpace: Number of bytes of space available on each sibling.
**
*/
usableSpace = pBt->usableSize - 12 + leafCorrection;
for(i=k=0; i<nOld; i++, k++){
MemPage *p = apOld[i];
b.apEnd[k] = p->aDataEnd;
b.ixNx[k] = cntOld[i];
if( k && b.ixNx[k]==b.ixNx[k-1] ){
k--; /* Omit b.ixNx[] entry for child pages with no cells */
}
if( !leafData ){
k++;
b.apEnd[k] = pParent->aDataEnd;
b.ixNx[k] = cntOld[i]+1;
}
assert( p->nFree>=0 );
szNew[i] = usableSpace - p->nFree;
for(j=0; j<p->nOverflow; j++){
szNew[i] += 2 + p->xCellSize(p, p->apOvfl[j]);
}
cntNew[i] = cntOld[i];
}
k = nOld;
for(i=0; i<k; i++){
int sz;
while( szNew[i]>usableSpace ){
if( i+1>=k ){
k = i+2;
if( k>NB+2 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
szNew[k-1] = 0;
cntNew[k-1] = b.nCell;
}
sz = 2 + cachedCellSize(&b, cntNew[i]-1);
szNew[i] -= sz;
if( !leafData ){
if( cntNew[i]<b.nCell ){
sz = 2 + cachedCellSize(&b, cntNew[i]);
}else{
sz = 0;
}
}
szNew[i+1] += sz;
cntNew[i]--;
}
while( cntNew[i]<b.nCell ){
sz = 2 + cachedCellSize(&b, cntNew[i]);
if( szNew[i]+sz>usableSpace ) break;
szNew[i] += sz;
cntNew[i]++;
if( !leafData ){
if( cntNew[i]<b.nCell ){
sz = 2 + cachedCellSize(&b, cntNew[i]);
}else{
sz = 0;
}
}
szNew[i+1] -= sz;
}
if( cntNew[i]>=b.nCell ){
k = i+1;
}else if( cntNew[i] <= (i>0 ? cntNew[i-1] : 0) ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
}
/*
** The packing computed by the previous block is biased toward the siblings
** on the left side (siblings with smaller keys). The left siblings are
** always nearly full, while the right-most sibling might be nearly empty.
** The next block of code attempts to adjust the packing of siblings to
** get a better balance.
**
** This adjustment is more than an optimization. The packing above might
** be so out of balance as to be illegal. For example, the right-most
** sibling might be completely empty. This adjustment is not optional.
*/
for(i=k-1; i>0; i--){
int szRight = szNew[i]; /* Size of sibling on the right */
int szLeft = szNew[i-1]; /* Size of sibling on the left */
int r; /* Index of right-most cell in left sibling */
int d; /* Index of first cell to the left of right sibling */
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
(void)cachedCellSize(&b, d);
do{
assert( d<nMaxCells );
assert( r<nMaxCells );
(void)cachedCellSize(&b, r);
if( szRight!=0
&& (bBulk || szRight+b.szCell[d]+2 > szLeft-(b.szCell[r]+(i==k-1?0:2)))){
break;
}
szRight += b.szCell[d] + 2;
szLeft -= b.szCell[r] + 2;
cntNew[i-1] = r;
r--;
d--;
}while( r>=0 );
szNew[i] = szRight;
szNew[i-1] = szLeft;
if( cntNew[i-1] <= (i>1 ? cntNew[i-2] : 0) ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
}
/* Sanity check: For a non-corrupt database file one of the follwing
** must be true:
** (1) We found one or more cells (cntNew[0])>0), or
** (2) pPage is a virtual root page. A virtual root page is when
** the real root page is page 1 and we are the only child of
** that page.
*/
assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) || CORRUPT_DB);
TRACE(("BALANCE: old: %d(nc=%d) %d(nc=%d) %d(nc=%d)\n",
apOld[0]->pgno, apOld[0]->nCell,
nOld>=2 ? apOld[1]->pgno : 0, nOld>=2 ? apOld[1]->nCell : 0,
nOld>=3 ? apOld[2]->pgno : 0, nOld>=3 ? apOld[2]->nCell : 0
));
/*
** Allocate k new pages. Reuse old pages where possible.
*/
pageFlags = apOld[0]->aData[0];
for(i=0; i<k; i++){
MemPage *pNew;
if( i<nOld ){
pNew = apNew[i] = apOld[i];
apOld[i] = 0;
rc = sqlite3PagerWrite(pNew->pDbPage);
nNew++;
if( sqlite3PagerPageRefcount(pNew->pDbPage)!=1+(i==(iParentIdx-nxDiv)) ){
rc = SQLITE_CORRUPT_BKPT;
}
if( rc ) goto balance_cleanup;
}else{
assert( i>0 );
rc = allocateBtreePage(pBt, &pNew, &pgno, (bBulk ? 1 : pgno), 0);
if( rc ) goto balance_cleanup;
zeroPage(pNew, pageFlags);
apNew[i] = pNew;
nNew++;
cntOld[i] = b.nCell;
/* Set the pointer-map entry for the new sibling page. */
if( ISAUTOVACUUM ){
ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno, &rc);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}
}
/*
** Reassign page numbers so that the new pages are in ascending order.
** This helps to keep entries in the disk file in order so that a scan
** of the table is closer to a linear scan through the file. That in turn
** helps the operating system to deliver pages from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since n is never more
** than (NB+2) (a small constant), that should not be a problem.
**
** When NB==3, this one optimization makes the database about 25% faster
** for large insertions and deletions.
*/
for(i=0; i<nNew; i++){
aPgOrder[i] = aPgno[i] = apNew[i]->pgno;
aPgFlags[i] = apNew[i]->pDbPage->flags;
for(j=0; j<i; j++){
if( NEVER(aPgno[j]==aPgno[i]) ){
/* This branch is taken if the set of sibling pages somehow contains
** duplicate entries. This can happen if the database is corrupt.
** It would be simpler to detect this as part of the loop below, but
** we do the detection here in order to avoid populating the pager
** cache with two separate objects associated with the same
** page number. */
assert( CORRUPT_DB );
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
}
}
for(i=0; i<nNew; i++){
int iBest = 0; /* aPgno[] index of page number to use */
for(j=1; j<nNew; j++){
if( aPgOrder[j]<aPgOrder[iBest] ) iBest = j;
}
pgno = aPgOrder[iBest];
aPgOrder[iBest] = 0xffffffff;
if( iBest!=i ){
if( iBest>i ){
sqlite3PagerRekey(apNew[iBest]->pDbPage, pBt->nPage+iBest+1, 0);
}
sqlite3PagerRekey(apNew[i]->pDbPage, pgno, aPgFlags[iBest]);
apNew[i]->pgno = pgno;
}
}
TRACE(("BALANCE: new: %d(%d nc=%d) %d(%d nc=%d) %d(%d nc=%d) "
"%d(%d nc=%d) %d(%d nc=%d)\n",
apNew[0]->pgno, szNew[0], cntNew[0],
nNew>=2 ? apNew[1]->pgno : 0, nNew>=2 ? szNew[1] : 0,
nNew>=2 ? cntNew[1] - cntNew[0] - !leafData : 0,
nNew>=3 ? apNew[2]->pgno : 0, nNew>=3 ? szNew[2] : 0,
nNew>=3 ? cntNew[2] - cntNew[1] - !leafData : 0,
nNew>=4 ? apNew[3]->pgno : 0, nNew>=4 ? szNew[3] : 0,
nNew>=4 ? cntNew[3] - cntNew[2] - !leafData : 0,
nNew>=5 ? apNew[4]->pgno : 0, nNew>=5 ? szNew[4] : 0,
nNew>=5 ? cntNew[4] - cntNew[3] - !leafData : 0
));
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
assert( nNew>=1 && nNew<=ArraySize(apNew) );
assert( apNew[nNew-1]!=0 );
put4byte(pRight, apNew[nNew-1]->pgno);
/* If the sibling pages are not leaves, ensure that the right-child pointer
** of the right-most new sibling page is set to the value that was
** originally in the same field of the right-most old sibling page. */
if( (pageFlags & PTF_LEAF)==0 && nOld!=nNew ){
MemPage *pOld = (nNew>nOld ? apNew : apOld)[nOld-1];
memcpy(&apNew[nNew-1]->aData[8], &pOld->aData[8], 4);
}
/* Make any required updates to pointer map entries associated with
** cells stored on sibling pages following the balance operation. Pointer
** map entries associated with divider cells are set by the insertCell()
** routine. The associated pointer map entries are:
**
** a) if the cell contains a reference to an overflow chain, the
** entry associated with the first page in the overflow chain, and
**
** b) if the sibling pages are not leaves, the child page associated
** with the cell.
**
** If the sibling pages are not leaves, then the pointer map entry
** associated with the right-child of each sibling may also need to be
** updated. This happens below, after the sibling pages have been
** populated, not here.
*/
if( ISAUTOVACUUM ){
MemPage *pOld;
MemPage *pNew = pOld = apNew[0];
int cntOldNext = pNew->nCell + pNew->nOverflow;
int iNew = 0;
int iOld = 0;
for(i=0; i<b.nCell; i++){
u8 *pCell = b.apCell[i];
while( i==cntOldNext ){
iOld++;
assert( iOld<nNew || iOld<nOld );
assert( iOld>=0 && iOld<NB );
pOld = iOld<nNew ? apNew[iOld] : apOld[iOld];
cntOldNext += pOld->nCell + pOld->nOverflow + !leafData;
}
if( i==cntNew[iNew] ){
pNew = apNew[++iNew];
if( !leafData ) continue;
}
/* Cell pCell is destined for new sibling page pNew. Originally, it
** was either part of sibling page iOld (possibly an overflow cell),
** or else the divider cell to the left of sibling page iOld. So,
** if sibling page iOld had the same page number as pNew, and if
** pCell really was a part of sibling page iOld (not a divider or
** overflow cell), we can skip updating the pointer map entries. */
if( iOld>=nNew
|| pNew->pgno!=aPgno[iOld]
|| !SQLITE_WITHIN(pCell,pOld->aData,pOld->aDataEnd)
){
if( !leafCorrection ){
ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno, &rc);
}
if( cachedCellSize(&b,i)>pNew->minLocal ){
ptrmapPutOvflPtr(pNew, pOld, pCell, &rc);
}
if( rc ) goto balance_cleanup;
}
}
}
/* Insert new divider cells into pParent. */
for(i=0; i<nNew-1; i++){
u8 *pCell;
u8 *pTemp;
int sz;
MemPage *pNew = apNew[i];
j = cntNew[i];
assert( j<nMaxCells );
assert( b.apCell[j]!=0 );
pCell = b.apCell[j];
sz = b.szCell[j] + leafCorrection;
pTemp = &aOvflSpace[iOvflSpace];
if( !pNew->leaf ){
memcpy(&pNew->aData[8], pCell, 4);
}else if( leafData ){
/* If the tree is a leaf-data tree, and the siblings are leaves,
** then there is no divider cell in b.apCell[]. Instead, the divider
** cell consists of the integer key for the right-most cell of
** the sibling-page assembled above only.
*/
CellInfo info;
j--;
pNew->xParseCell(pNew, b.apCell[j], &info);
pCell = pTemp;
sz = 4 + putVarint(&pCell[4], info.nKey);
pTemp = 0;
}else{
pCell -= 4;
/* Obscure case for non-leaf-data trees: If the cell at pCell was
** previously stored on a leaf node, and its reported size was 4
** bytes, then it may actually be smaller than this
** (see btreeParseCellPtr(), 4 bytes is the minimum size of
** any cell). But it is important to pass the correct size to
** insertCell(), so reparse the cell now.
**
** This can only happen for b-trees used to evaluate "IN (SELECT ...)"
** and WITHOUT ROWID tables with exactly one column which is the
** primary key.
*/
if( b.szCell[j]==4 ){
assert(leafCorrection==4);
sz = pParent->xCellSize(pParent, pCell);
}
}
iOvflSpace += sz;
assert( sz<=pBt->maxLocal+23 );
assert( iOvflSpace <= (int)pBt->pageSize );
insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno, &rc);
if( rc!=SQLITE_OK ) goto balance_cleanup;
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
}
/* Now update the actual sibling pages. The order in which they are updated
** is important, as this code needs to avoid disrupting any page from which
** cells may still to be read. In practice, this means:
**
** (1) If cells are moving left (from apNew[iPg] to apNew[iPg-1])
** then it is not safe to update page apNew[iPg] until after
** the left-hand sibling apNew[iPg-1] has been updated.
**
** (2) If cells are moving right (from apNew[iPg] to apNew[iPg+1])
** then it is not safe to update page apNew[iPg] until after
** the right-hand sibling apNew[iPg+1] has been updated.
**
** If neither of the above apply, the page is safe to update.
**
** The iPg value in the following loop starts at nNew-1 goes down
** to 0, then back up to nNew-1 again, thus making two passes over
** the pages. On the initial downward pass, only condition (1) above
** needs to be tested because (2) will always be true from the previous
** step. On the upward pass, both conditions are always true, so the
** upwards pass simply processes pages that were missed on the downward
** pass.
*/
for(i=1-nNew; i<nNew; i++){
int iPg = i<0 ? -i : i;
assert( iPg>=0 && iPg<nNew );
if( abDone[iPg] ) continue; /* Skip pages already processed */
if( i>=0 /* On the upwards pass, or... */
|| cntOld[iPg-1]>=cntNew[iPg-1] /* Condition (1) is true */
){
int iNew;
int iOld;
int nNewCell;
/* Verify condition (1): If cells are moving left, update iPg
** only after iPg-1 has already been updated. */
assert( iPg==0 || cntOld[iPg-1]>=cntNew[iPg-1] || abDone[iPg-1] );
/* Verify condition (2): If cells are moving right, update iPg
** only after iPg+1 has already been updated. */
assert( cntNew[iPg]>=cntOld[iPg] || abDone[iPg+1] );
if( iPg==0 ){
iNew = iOld = 0;
nNewCell = cntNew[0];
}else{
iOld = iPg<nOld ? (cntOld[iPg-1] + !leafData) : b.nCell;
iNew = cntNew[iPg-1] + !leafData;
nNewCell = cntNew[iPg] - iNew;
}
rc = editPage(apNew[iPg], iOld, iNew, nNewCell, &b);
if( rc ) goto balance_cleanup;
abDone[iPg]++;
apNew[iPg]->nFree = usableSpace-szNew[iPg];
assert( apNew[iPg]->nOverflow==0 );
assert( apNew[iPg]->nCell==nNewCell );
}
}
/* All pages have been processed exactly once */
assert( memcmp(abDone, "\01\01\01\01\01", nNew)==0 );
assert( nOld>0 );
assert( nNew>0 );
if( isRoot && pParent->nCell==0 && pParent->hdrOffset<=apNew[0]->nFree ){
/* The root page of the b-tree now contains no cells. The only sibling
** page is the right-child of the parent. Copy the contents of the
** child page into the parent, decreasing the overall height of the
** b-tree structure by one. This is described as the "balance-shallower"
** sub-algorithm in some documentation.
**
** If this is an auto-vacuum database, the call to copyNodeContent()
** sets all pointer-map entries corresponding to database image pages
** for which the pointer is stored within the content being copied.
**
** It is critical that the child page be defragmented before being
** copied into the parent, because if the parent is page 1 then it will
** by smaller than the child due to the database header, and so all the
** free space needs to be up front.
*/
assert( nNew==1 || CORRUPT_DB );
rc = defragmentPage(apNew[0], -1);
testcase( rc!=SQLITE_OK );
assert( apNew[0]->nFree ==
(get2byteNotZero(&apNew[0]->aData[5]) - apNew[0]->cellOffset
- apNew[0]->nCell*2)
|| rc!=SQLITE_OK
);
copyNodeContent(apNew[0], pParent, &rc);
freePage(apNew[0], &rc);
}else if( ISAUTOVACUUM && !leafCorrection ){
/* Fix the pointer map entries associated with the right-child of each
** sibling page. All other pointer map entries have already been taken
** care of. */
for(i=0; i<nNew; i++){
u32 key = get4byte(&apNew[i]->aData[8]);
ptrmapPut(pBt, key, PTRMAP_BTREE, apNew[i]->pgno, &rc);
}
}
assert( pParent->isInit );
TRACE(("BALANCE: finished: old=%d new=%d cells=%d\n",
nOld, nNew, b.nCell));
/* Free any old pages that were not reused as new pages.
*/
for(i=nNew; i<nOld; i++){
freePage(apOld[i], &rc);
}
#if 0
if( ISAUTOVACUUM && rc==SQLITE_OK && apNew[0]->isInit ){
/* The ptrmapCheckPages() contains assert() statements that verify that
** all pointer map pages are set correctly. This is helpful while
** debugging. This is usually disabled because a corrupt database may
** cause an assert() statement to fail. */
ptrmapCheckPages(apNew, nNew);
ptrmapCheckPages(&pParent, 1);
}
#endif
/*
** Cleanup before returning.
*/
balance_cleanup:
sqlite3StackFree(0, b.apCell);
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
}
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
return rc;
}
/*
** This function is called when the root page of a b-tree structure is
** overfull (has one or more overflow pages).
**
** A new child page is allocated and the contents of the current root
** page, including overflow cells, are copied into the child. The root
** page is then overwritten to make it an empty page with the right-child
** pointer pointing to the new page.
**
** Before returning, all pointer-map entries corresponding to pages
** that the new child-page now contains pointers to are updated. The
** entry corresponding to the new right-child pointer of the root
** page is also updated.
**
** If successful, *ppChild is set to contain a reference to the child
** page and SQLITE_OK is returned. In this case the caller is required
** to call releasePage() on *ppChild exactly once. If an error occurs,
** an error code is returned and *ppChild is set to 0.
*/
static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
int rc; /* Return value from subprocedures */
MemPage *pChild = 0; /* Pointer to a new child page */
Pgno pgnoChild = 0; /* Page number of the new child page */
BtShared *pBt = pRoot->pBt; /* The BTree */
assert( pRoot->nOverflow>0 );
assert( sqlite3_mutex_held(pBt->mutex) );
/* Make pRoot, the root page of the b-tree, writable. Allocate a new
** page that will become the new right-child of pPage. Copy the contents
** of the node stored on pRoot into the new child page.
*/
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc==SQLITE_OK ){
rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0);
copyNodeContent(pRoot, pChild, &rc);
if( ISAUTOVACUUM ){
ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno, &rc);
}
}
if( rc ){
*ppChild = 0;
releasePage(pChild);
return rc;
}
assert( sqlite3PagerIswriteable(pChild->pDbPage) );
assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
assert( pChild->nCell==pRoot->nCell || CORRUPT_DB );
TRACE(("BALANCE: copy root %d into %d\n", pRoot->pgno, pChild->pgno));
/* Copy the overflow cells from pRoot to pChild */
memcpy(pChild->aiOvfl, pRoot->aiOvfl,
pRoot->nOverflow*sizeof(pRoot->aiOvfl[0]));
memcpy(pChild->apOvfl, pRoot->apOvfl,
pRoot->nOverflow*sizeof(pRoot->apOvfl[0]));
pChild->nOverflow = pRoot->nOverflow;
/* Zero the contents of pRoot. Then install pChild as the right-child. */
zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);
*ppChild = pChild;
return SQLITE_OK;
}
/*
** Return SQLITE_CORRUPT if any cursor other than pCur is currently valid
** on the same B-tree as pCur.
**
** This can if a database is corrupt with two or more SQL tables
** pointing to the same b-tree. If an insert occurs on one SQL table
** and causes a BEFORE TRIGGER to do a secondary insert on the other SQL
** table linked to the same b-tree. If the secondary insert causes a
** rebalance, that can change content out from under the cursor on the
** first SQL table, violating invariants on the first insert.
*/
static int anotherValidCursor(BtCursor *pCur){
BtCursor *pOther;
for(pOther=pCur->pBt->pCursor; pOther; pOther=pOther->pNext){
if( pOther!=pCur
&& pOther->eState==CURSOR_VALID
&& pOther->pPage==pCur->pPage
){
return SQLITE_CORRUPT_BKPT;
}
}
return SQLITE_OK;
}
/*
** The page that pCur currently points to has just been modified in
** some way. This function figures out if this modification means the
** tree needs to be balanced, and if so calls the appropriate balancing
** routine. Balancing routines are:
**
** balance_quick()
** balance_deeper()
** balance_nonroot()
*/
static int balance(BtCursor *pCur){
int rc = SQLITE_OK;
const int nMin = pCur->pBt->usableSize * 2 / 3;
u8 aBalanceQuickSpace[13];
u8 *pFree = 0;
VVA_ONLY( int balance_quick_called = 0 );
VVA_ONLY( int balance_deeper_called = 0 );
do {
int iPage;
MemPage *pPage = pCur->pPage;
if( NEVER(pPage->nFree<0) && btreeComputeFreeSpace(pPage) ) break;
if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
break;
}else if( (iPage = pCur->iPage)==0 ){
if( pPage->nOverflow && (rc = anotherValidCursor(pCur))==SQLITE_OK ){
/* The root page of the b-tree is overfull. In this case call the
** balance_deeper() function to create a new child for the root-page
** and copy the current contents of the root-page to it. The
** next iteration of the do-loop will balance the child page.
*/
assert( balance_deeper_called==0 );
VVA_ONLY( balance_deeper_called++ );
rc = balance_deeper(pPage, &pCur->apPage[1]);
if( rc==SQLITE_OK ){
pCur->iPage = 1;
pCur->ix = 0;
pCur->aiIdx[0] = 0;
pCur->apPage[0] = pPage;
pCur->pPage = pCur->apPage[1];
assert( pCur->pPage->nOverflow );
}
}else{
break;
}
}else{
MemPage * const pParent = pCur->apPage[iPage-1];
int const iIdx = pCur->aiIdx[iPage-1];
rc = sqlite3PagerWrite(pParent->pDbPage);
if( rc==SQLITE_OK && pParent->nFree<0 ){
rc = btreeComputeFreeSpace(pParent);
}
if( rc==SQLITE_OK ){
#ifndef SQLITE_OMIT_QUICKBALANCE
if( pPage->intKeyLeaf
&& pPage->nOverflow==1
&& pPage->aiOvfl[0]==pPage->nCell
&& pParent->pgno!=1
&& pParent->nCell==iIdx
){
/* Call balance_quick() to create a new sibling of pPage on which
** to store the overflow cell. balance_quick() inserts a new cell
** into pParent, which may cause pParent overflow. If this
** happens, the next iteration of the do-loop will balance pParent
** use either balance_nonroot() or balance_deeper(). Until this
** happens, the overflow cell is stored in the aBalanceQuickSpace[]
** buffer.
**
** The purpose of the following assert() is to check that only a
** single call to balance_quick() is made for each call to this
** function. If this were not verified, a subtle bug involving reuse
** of the aBalanceQuickSpace[] might sneak in.
*/
assert( balance_quick_called==0 );
VVA_ONLY( balance_quick_called++ );
rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
}else
#endif
{
/* In this case, call balance_nonroot() to redistribute cells
** between pPage and up to 2 of its sibling pages. This involves
** modifying the contents of pParent, which may cause pParent to
** become overfull or underfull. The next iteration of the do-loop
** will balance the parent page to correct this.
**
** If the parent page becomes overfull, the overflow cell or cells
** are stored in the pSpace buffer allocated immediately below.
** A subsequent iteration of the do-loop will deal with this by
** calling balance_nonroot() (balance_deeper() may be called first,
** but it doesn't deal with overflow cells - just moves them to a
** different page). Once this subsequent call to balance_nonroot()
** has completed, it is safe to release the pSpace buffer used by
** the previous call, as the overflow cell data will have been
** copied either into the body of a database page or into the new
** pSpace buffer passed to the latter call to balance_nonroot().
*/
u8 *pSpace = sqlite3PageMalloc(pCur->pBt->pageSize);
rc = balance_nonroot(pParent, iIdx, pSpace, iPage==1,
pCur->hints&BTREE_BULKLOAD);
if( pFree ){
/* If pFree is not NULL, it points to the pSpace buffer used
** by a previous call to balance_nonroot(). Its contents are
** now stored either on real database pages or within the
** new pSpace buffer, so it may be safely freed here. */
sqlite3PageFree(pFree);
}
/* The pSpace buffer will be freed after the next call to
** balance_nonroot(), or just before this function returns, whichever
** comes first. */
pFree = pSpace;
}
}
pPage->nOverflow = 0;
/* The next iteration of the do-loop balances the parent page. */
releasePage(pPage);
pCur->iPage--;
assert( pCur->iPage>=0 );
pCur->pPage = pCur->apPage[pCur->iPage];
}
}while( rc==SQLITE_OK );
if( pFree ){
sqlite3PageFree(pFree);
}
return rc;
}
/* Overwrite content from pX into pDest. Only do the write if the
** content is different from what is already there.
*/
static int btreeOverwriteContent(
MemPage *pPage, /* MemPage on which writing will occur */
u8 *pDest, /* Pointer to the place to start writing */
const BtreePayload *pX, /* Source of data to write */
int iOffset, /* Offset of first byte to write */
int iAmt /* Number of bytes to be written */
){
int nData = pX->nData - iOffset;
if( nData<=0 ){
/* Overwritting with zeros */
int i;
for(i=0; i<iAmt && pDest[i]==0; i++){}
if( i<iAmt ){
int rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
memset(pDest + i, 0, iAmt - i);
}
}else{
if( nData<iAmt ){
/* Mixed read data and zeros at the end. Make a recursive call
** to write the zeros then fall through to write the real data */
int rc = btreeOverwriteContent(pPage, pDest+nData, pX, iOffset+nData,
iAmt-nData);
if( rc ) return rc;
iAmt = nData;
}
if( memcmp(pDest, ((u8*)pX->pData) + iOffset, iAmt)!=0 ){
int rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
/* In a corrupt database, it is possible for the source and destination
** buffers to overlap. This is harmless since the database is already
** corrupt but it does cause valgrind and ASAN warnings. So use
** memmove(). */
memmove(pDest, ((u8*)pX->pData) + iOffset, iAmt);
}
}
return SQLITE_OK;
}
/*
** Overwrite the cell that cursor pCur is pointing to with fresh content
** contained in pX.
*/
static int btreeOverwriteCell(BtCursor *pCur, const BtreePayload *pX){
int iOffset; /* Next byte of pX->pData to write */
int nTotal = pX->nData + pX->nZero; /* Total bytes of to write */
int rc; /* Return code */
MemPage *pPage = pCur->pPage; /* Page being written */
BtShared *pBt; /* Btree */
Pgno ovflPgno; /* Next overflow page to write */
u32 ovflPageSize; /* Size to write on overflow page */
if( pCur->info.pPayload + pCur->info.nLocal > pPage->aDataEnd
|| pCur->info.pPayload < pPage->aData + pPage->cellOffset
){
return SQLITE_CORRUPT_BKPT;
}
/* Overwrite the local portion first */
rc = btreeOverwriteContent(pPage, pCur->info.pPayload, pX,
0, pCur->info.nLocal);
if( rc ) return rc;
if( pCur->info.nLocal==nTotal ) return SQLITE_OK;
/* Now overwrite the overflow pages */
iOffset = pCur->info.nLocal;
assert( nTotal>=0 );
assert( iOffset>=0 );
ovflPgno = get4byte(pCur->info.pPayload + iOffset);
pBt = pPage->pBt;
ovflPageSize = pBt->usableSize - 4;
do{
rc = btreeGetPage(pBt, ovflPgno, &pPage, 0);
if( rc ) return rc;
if( sqlite3PagerPageRefcount(pPage->pDbPage)!=1 ){
rc = SQLITE_CORRUPT_BKPT;
}else{
if( iOffset+ovflPageSize<(u32)nTotal ){
ovflPgno = get4byte(pPage->aData);
}else{
ovflPageSize = nTotal - iOffset;
}
rc = btreeOverwriteContent(pPage, pPage->aData+4, pX,
iOffset, ovflPageSize);
}
sqlite3PagerUnref(pPage->pDbPage);
if( rc ) return rc;
iOffset += ovflPageSize;
}while( iOffset<nTotal );
return SQLITE_OK;
}
/*
** Insert a new record into the BTree. The content of the new record
** is described by the pX object. The pCur cursor is used only to
** define what table the record should be inserted into, and is left
** pointing at a random location.
**
** For a table btree (used for rowid tables), only the pX.nKey value of
** the key is used. The pX.pKey value must be NULL. The pX.nKey is the
** rowid or INTEGER PRIMARY KEY of the row. The pX.nData,pData,nZero fields
** hold the content of the row.
**
** For an index btree (used for indexes and WITHOUT ROWID tables), the
** key is an arbitrary byte sequence stored in pX.pKey,nKey. The
** pX.pData,nData,nZero fields must be zero.
**
** If the seekResult parameter is non-zero, then a successful call to
** MovetoUnpacked() to seek cursor pCur to (pKey,nKey) has already
** been performed. In other words, if seekResult!=0 then the cursor
** is currently pointing to a cell that will be adjacent to the cell
** to be inserted. If seekResult<0 then pCur points to a cell that is
** smaller then (pKey,nKey). If seekResult>0 then pCur points to a cell
** that is larger than (pKey,nKey).
**
** If seekResult==0, that means pCur is pointing at some unknown location.
** In that case, this routine must seek the cursor to the correct insertion
** point for (pKey,nKey) before doing the insertion. For index btrees,
** if pX->nMem is non-zero, then pX->aMem contains pointers to the unpacked
** key values and pX->aMem can be used instead of pX->pKey to avoid having
** to decode the key.
*/
int sqlite3BtreeInsert(
BtCursor *pCur, /* Insert data into the table of this cursor */
const BtreePayload *pX, /* Content of the row to be inserted */
int flags, /* True if this is likely an append */
int seekResult /* Result of prior MovetoUnpacked() call */
){
int rc;
int loc = seekResult; /* -1: before desired location +1: after */
int szNew = 0;
int idx;
MemPage *pPage;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
unsigned char *oldCell;
unsigned char *newCell = 0;
assert( (flags & (BTREE_SAVEPOSITION|BTREE_APPEND|BTREE_PREFORMAT))==flags );
assert( (flags & BTREE_PREFORMAT)==0 || seekResult || pCur->pKeyInfo==0 );
if( pCur->eState==CURSOR_FAULT ){
assert( pCur->skipNext!=SQLITE_OK );
return pCur->skipNext;
}
assert( cursorOwnsBtShared(pCur) );
assert( (pCur->curFlags & BTCF_WriteFlag)!=0
&& pBt->inTransaction==TRANS_WRITE
&& (pBt->btsFlags & BTS_READ_ONLY)==0 );
assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
/* Assert that the caller has been consistent. If this cursor was opened
** expecting an index b-tree, then the caller should be inserting blob
** keys with no associated data. If the cursor was opened expecting an
** intkey table, the caller should be inserting integer keys with a
** blob of associated data. */
assert( (flags & BTREE_PREFORMAT) || (pX->pKey==0)==(pCur->pKeyInfo==0) );
/* Save the positions of any other cursors open on this table.
**
** In some cases, the call to btreeMoveto() below is a no-op. For
** example, when inserting data into a table with auto-generated integer
** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the
** integer key to use. It then calls this function to actually insert the
** data into the intkey B-Tree. In this case btreeMoveto() recognizes
** that the cursor is already where it needs to be and returns without
** doing any work. To avoid thwarting these optimizations, it is important
** not to clear the cursor here.
*/
if( pCur->curFlags & BTCF_Multiple ){
rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
if( rc ) return rc;
}
if( pCur->pKeyInfo==0 ){
assert( pX->pKey==0 );
/* If this is an insert into a table b-tree, invalidate any incrblob
** cursors open on the row being replaced */
invalidateIncrblobCursors(p, pCur->pgnoRoot, pX->nKey, 0);
/* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
** to a row with the same key as the new entry being inserted.
*/
#ifdef SQLITE_DEBUG
if( flags & BTREE_SAVEPOSITION ){
assert( pCur->curFlags & BTCF_ValidNKey );
assert( pX->nKey==pCur->info.nKey );
assert( loc==0 );
}
#endif
/* On the other hand, BTREE_SAVEPOSITION==0 does not imply
** that the cursor is not pointing to a row to be overwritten.
** So do a complete check.
*/
if( (pCur->curFlags&BTCF_ValidNKey)!=0 && pX->nKey==pCur->info.nKey ){
/* The cursor is pointing to the entry that is to be
** overwritten */
assert( pX->nData>=0 && pX->nZero>=0 );
if( pCur->info.nSize!=0
&& pCur->info.nPayload==(u32)pX->nData+pX->nZero
){
/* New entry is the same size as the old. Do an overwrite */
return btreeOverwriteCell(pCur, pX);
}
assert( loc==0 );
}else if( loc==0 ){
/* The cursor is *not* pointing to the cell to be overwritten, nor
** to an adjacent cell. Move the cursor so that it is pointing either
** to the cell to be overwritten or an adjacent cell.
*/
rc = sqlite3BtreeMovetoUnpacked(pCur, 0, pX->nKey, flags!=0, &loc);
if( rc ) return rc;
}
}else{
/* This is an index or a WITHOUT ROWID table */
/* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
** to a row with the same key as the new entry being inserted.
*/
assert( (flags & BTREE_SAVEPOSITION)==0 || loc==0 );
/* If the cursor is not already pointing either to the cell to be
** overwritten, or if a new cell is being inserted, if the cursor is
** not pointing to an immediately adjacent cell, then move the cursor
** so that it does.
*/
if( loc==0 && (flags & BTREE_SAVEPOSITION)==0 ){
if( pX->nMem ){
UnpackedRecord r;
r.pKeyInfo = pCur->pKeyInfo;
r.aMem = pX->aMem;
r.nField = pX->nMem;
r.default_rc = 0;
r.errCode = 0;
r.r1 = 0;
r.r2 = 0;
r.eqSeen = 0;
rc = sqlite3BtreeMovetoUnpacked(pCur, &r, 0, flags!=0, &loc);
}else{
rc = btreeMoveto(pCur, pX->pKey, pX->nKey, flags!=0, &loc);
}
if( rc ) return rc;
}
/* If the cursor is currently pointing to an entry to be overwritten
** and the new content is the same as as the old, then use the
** overwrite optimization.
*/
if( loc==0 ){
getCellInfo(pCur);
if( pCur->info.nKey==pX->nKey ){
BtreePayload x2;
x2.pData = pX->pKey;
x2.nData = pX->nKey;
x2.nZero = 0;
return btreeOverwriteCell(pCur, &x2);
}
}
}
assert( pCur->eState==CURSOR_VALID
|| (pCur->eState==CURSOR_INVALID && loc)
|| CORRUPT_DB );
pPage = pCur->pPage;
assert( pPage->intKey || pX->nKey>=0 || (flags & BTREE_PREFORMAT) );
assert( pPage->leaf || !pPage->intKey );
if( pPage->nFree<0 ){
if( pCur->eState>CURSOR_INVALID ){
rc = SQLITE_CORRUPT_BKPT;
}else{
rc = btreeComputeFreeSpace(pPage);
}
if( rc ) return rc;
}
TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
pCur->pgnoRoot, pX->nKey, pX->nData, pPage->pgno,
loc==0 ? "overwrite" : "new entry"));
assert( pPage->isInit );
newCell = pBt->pTmpSpace;
assert( newCell!=0 );
if( flags & BTREE_PREFORMAT ){
rc = SQLITE_OK;
szNew = pBt->nPreformatSize;
if( szNew<4 ) szNew = 4;
if( ISAUTOVACUUM && szNew>pPage->maxLocal ){
CellInfo info;
pPage->xParseCell(pPage, newCell, &info);
if( info.nPayload!=info.nLocal ){
Pgno ovfl = get4byte(&newCell[szNew-4]);
ptrmapPut(pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, &rc);
}
}
}else{
rc = fillInCell(pPage, newCell, pX, &szNew);
}
if( rc ) goto end_insert;
assert( szNew==pPage->xCellSize(pPage, newCell) );
assert( szNew <= MX_CELL_SIZE(pBt) );
idx = pCur->ix;
if( loc==0 ){
CellInfo info;
assert( idx<pPage->nCell );
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ){
goto end_insert;
}
oldCell = findCell(pPage, idx);
if( !pPage->leaf ){
memcpy(newCell, oldCell, 4);
}
rc = clearCell(pPage, oldCell, &info);
testcase( pCur->curFlags & BTCF_ValidOvfl );
invalidateOverflowCache(pCur);
if( info.nSize==szNew && info.nLocal==info.nPayload
&& (!ISAUTOVACUUM || szNew<pPage->minLocal)
){
/* Overwrite the old cell with the new if they are the same size.
** We could also try to do this if the old cell is smaller, then add
** the leftover space to the free list. But experiments show that
** doing that is no faster then skipping this optimization and just
** calling dropCell() and insertCell().
**
** This optimization cannot be used on an autovacuum database if the
** new entry uses overflow pages, as the insertCell() call below is
** necessary to add the PTRMAP_OVERFLOW1 pointer-map entry. */
assert( rc==SQLITE_OK ); /* clearCell never fails when nLocal==nPayload */
if( oldCell < pPage->aData+pPage->hdrOffset+10 ){
return SQLITE_CORRUPT_BKPT;
}
if( oldCell+szNew > pPage->aDataEnd ){
return SQLITE_CORRUPT_BKPT;
}
memcpy(oldCell, newCell, szNew);
return SQLITE_OK;
}
dropCell(pPage, idx, info.nSize, &rc);
if( rc ) goto end_insert;
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
idx = ++pCur->ix;
pCur->curFlags &= ~BTCF_ValidNKey;
}else{
assert( pPage->leaf );
}
insertCell(pPage, idx, newCell, szNew, 0, 0, &rc);
assert( pPage->nOverflow==0 || rc==SQLITE_OK );
assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );
/* If no error has occurred and pPage has an overflow cell, call balance()
** to redistribute the cells within the tree. Since balance() may move
** the cursor, zero the BtCursor.info.nSize and BTCF_ValidNKey
** variables.
**
** Previous versions of SQLite called moveToRoot() to move the cursor
** back to the root page as balance() used to invalidate the contents
** of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that,
** set the cursor state to "invalid". This makes common insert operations
** slightly faster.
**
** There is a subtle but important optimization here too. When inserting
** multiple records into an intkey b-tree using a single cursor (as can
** happen while processing an "INSERT INTO ... SELECT" statement), it
** is advantageous to leave the cursor pointing to the last entry in
** the b-tree if possible. If the cursor is left pointing to the last
** entry in the table, and the next row inserted has an integer key
** larger than the largest existing key, it is possible to insert the
** row without seeking the cursor. This can be a big performance boost.
*/
pCur->info.nSize = 0;
if( pPage->nOverflow ){
assert( rc==SQLITE_OK );
pCur->curFlags &= ~(BTCF_ValidNKey);
rc = balance(pCur);
/* Must make sure nOverflow is reset to zero even if the balance()
** fails. Internal data structure corruption will result otherwise.
** Also, set the cursor state to invalid. This stops saveCursorPosition()
** from trying to save the current position of the cursor. */
pCur->pPage->nOverflow = 0;
pCur->eState = CURSOR_INVALID;
if( (flags & BTREE_SAVEPOSITION) && rc==SQLITE_OK ){
btreeReleaseAllCursorPages(pCur);
if( pCur->pKeyInfo ){
assert( pCur->pKey==0 );
pCur->pKey = sqlite3Malloc( pX->nKey );
if( pCur->pKey==0 ){
rc = SQLITE_NOMEM;
}else{
memcpy(pCur->pKey, pX->pKey, pX->nKey);
}
}
pCur->eState = CURSOR_REQUIRESEEK;
pCur->nKey = pX->nKey;
}
}
assert( pCur->iPage<0 || pCur->pPage->nOverflow==0 );
end_insert:
return rc;
}
/*
** This function is used as part of copying the current row from cursor
** pSrc into cursor pDest. If the cursors are open on intkey tables, then
** parameter iKey is used as the rowid value when the record is copied
** into pDest. Otherwise, the record is copied verbatim.
**
** This function does not actually write the new value to cursor pDest.
** Instead, it creates and populates any required overflow pages and
** writes the data for the new cell into the BtShared.pTmpSpace buffer
** for the destination database. The size of the cell, in bytes, is left
** in BtShared.nPreformatSize. The caller completes the insertion by
** calling sqlite3BtreeInsert() with the BTREE_PREFORMAT flag specified.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
int sqlite3BtreeTransferRow(BtCursor *pDest, BtCursor *pSrc, i64 iKey){
int rc = SQLITE_OK;
BtShared *pBt = pDest->pBt;
u8 *aOut = pBt->pTmpSpace; /* Pointer to next output buffer */
const u8 *aIn; /* Pointer to next input buffer */
u32 nIn; /* Size of input buffer aIn[] */
u32 nRem; /* Bytes of data still to copy */
getCellInfo(pSrc);
aOut += putVarint32(aOut, pSrc->info.nPayload);
if( pDest->pKeyInfo==0 ) aOut += putVarint(aOut, iKey);
nIn = pSrc->info.nLocal;
aIn = pSrc->info.pPayload;
if( aIn+nIn>pSrc->pPage->aDataEnd ){
return SQLITE_CORRUPT_BKPT;
}
nRem = pSrc->info.nPayload;
if( nIn==nRem && nIn<pDest->pPage->maxLocal ){
memcpy(aOut, aIn, nIn);
pBt->nPreformatSize = nIn + (aOut - pBt->pTmpSpace);
}else{
Pager *pSrcPager = pSrc->pBt->pPager;
u8 *pPgnoOut = 0;
Pgno ovflIn = 0;
DbPage *pPageIn = 0;
MemPage *pPageOut = 0;
u32 nOut; /* Size of output buffer aOut[] */
nOut = btreePayloadToLocal(pDest->pPage, pSrc->info.nPayload);
pBt->nPreformatSize = nOut + (aOut - pBt->pTmpSpace);
if( nOut<pSrc->info.nPayload ){
pPgnoOut = &aOut[nOut];
pBt->nPreformatSize += 4;
}
if( nRem>nIn ){
if( aIn+nIn+4>pSrc->pPage->aDataEnd ){
return SQLITE_CORRUPT_BKPT;
}
ovflIn = get4byte(&pSrc->info.pPayload[nIn]);
}
do {
nRem -= nOut;
do{
assert( nOut>0 );
if( nIn>0 ){
int nCopy = MIN(nOut, nIn);
memcpy(aOut, aIn, nCopy);
nOut -= nCopy;
nIn -= nCopy;
aOut += nCopy;
aIn += nCopy;
}
if( nOut>0 ){
sqlite3PagerUnref(pPageIn);
pPageIn = 0;
rc = sqlite3PagerGet(pSrcPager, ovflIn, &pPageIn, PAGER_GET_READONLY);
if( rc==SQLITE_OK ){
aIn = (const u8*)sqlite3PagerGetData(pPageIn);
ovflIn = get4byte(aIn);
aIn += 4;
nIn = pSrc->pBt->usableSize - 4;
}
}
}while( rc==SQLITE_OK && nOut>0 );
if( rc==SQLITE_OK && nRem>0 ){
Pgno pgnoNew;
MemPage *pNew = 0;
rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
put4byte(pPgnoOut, pgnoNew);
if( ISAUTOVACUUM && pPageOut ){
ptrmapPut(pBt, pgnoNew, PTRMAP_OVERFLOW2, pPageOut->pgno, &rc);
}
releasePage(pPageOut);
pPageOut = pNew;
if( pPageOut ){
pPgnoOut = pPageOut->aData;
put4byte(pPgnoOut, 0);
aOut = &pPgnoOut[4];
nOut = MIN(pBt->usableSize - 4, nRem);
}
}
}while( nRem>0 && rc==SQLITE_OK );
releasePage(pPageOut);
sqlite3PagerUnref(pPageIn);
}
return rc;
}
/*
** Delete the entry that the cursor is pointing to.
**
** If the BTREE_SAVEPOSITION bit of the flags parameter is zero, then
** the cursor is left pointing at an arbitrary location after the delete.
** But if that bit is set, then the cursor is left in a state such that
** the next call to BtreeNext() or BtreePrev() moves it to the same row
** as it would have been on if the call to BtreeDelete() had been omitted.
**
** The BTREE_AUXDELETE bit of flags indicates that is one of several deletes
** associated with a single table entry and its indexes. Only one of those
** deletes is considered the "primary" delete. The primary delete occurs
** on a cursor that is not a BTREE_FORDELETE cursor. All but one delete
** operation on non-FORDELETE cursors is tagged with the AUXDELETE flag.
** The BTREE_AUXDELETE bit is a hint that is not used by this implementation,
** but which might be used by alternative storage engines.
*/
int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
int rc; /* Return code */
MemPage *pPage; /* Page to delete cell from */
unsigned char *pCell; /* Pointer to cell to delete */
int iCellIdx; /* Index of cell to delete */
int iCellDepth; /* Depth of node containing pCell */
CellInfo info; /* Size of the cell being deleted */
int bSkipnext = 0; /* Leaf cursor in SKIPNEXT state */
u8 bPreserve = flags & BTREE_SAVEPOSITION; /* Keep cursor valid */
assert( cursorOwnsBtShared(pCur) );
assert( pBt->inTransaction==TRANS_WRITE );
assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
assert( pCur->curFlags & BTCF_WriteFlag );
assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
assert( !hasReadConflicts(p, pCur->pgnoRoot) );
assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );
if( pCur->eState==CURSOR_REQUIRESEEK ){
rc = btreeRestoreCursorPosition(pCur);
if( rc ) return rc;
}
assert( pCur->eState==CURSOR_VALID );
iCellDepth = pCur->iPage;
iCellIdx = pCur->ix;
pPage = pCur->pPage;
pCell = findCell(pPage, iCellIdx);
if( pPage->nFree<0 && btreeComputeFreeSpace(pPage) ) return SQLITE_CORRUPT;
/* If the bPreserve flag is set to true, then the cursor position must
** be preserved following this delete operation. If the current delete
** will cause a b-tree rebalance, then this is done by saving the cursor
** key and leaving the cursor in CURSOR_REQUIRESEEK state before
** returning.
**
** Or, if the current delete will not cause a rebalance, then the cursor
** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
** before or after the deleted entry. In this case set bSkipnext to true. */
if( bPreserve ){
if( !pPage->leaf
|| (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
|| pPage->nCell==1 /* See dbfuzz001.test for a test case */
){
/* A b-tree rebalance will be required after deleting this entry.
** Save the cursor key. */
rc = saveCursorKey(pCur);
if( rc ) return rc;
}else{
bSkipnext = 1;
}
}
/* If the page containing the entry to delete is not a leaf page, move
** the cursor to the largest entry in the tree that is smaller than
** the entry being deleted. This cell will replace the cell being deleted
** from the internal node. The 'previous' entry is used for this instead
** of the 'next' entry, as the previous entry is always a part of the
** sub-tree headed by the child page of the cell being deleted. This makes
** balancing the tree following the delete operation easier. */
if( !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, 0);
assert( rc!=SQLITE_DONE );
if( rc ) return rc;
}
/* Save the positions of any other cursors open on this table before
** making any modifications. */
if( pCur->curFlags & BTCF_Multiple ){
rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
if( rc ) return rc;
}
/* If this is a delete operation to remove a row from a table b-tree,
** invalidate any incrblob cursors open on the row being deleted. */
if( pCur->pKeyInfo==0 ){
invalidateIncrblobCursors(p, pCur->pgnoRoot, pCur->info.nKey, 0);
}
/* Make the page containing the entry to be deleted writable. Then free any
** overflow pages associated with the entry and finally remove the cell
** itself from within the page. */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
rc = clearCell(pPage, pCell, &info);
dropCell(pPage, iCellIdx, info.nSize, &rc);
if( rc ) return rc;
/* If the cell deleted was not located on a leaf page, then the cursor
** is currently pointing to the largest entry in the sub-tree headed
** by the child-page of the cell that was just deleted from an internal
** node. The cell from the leaf node needs to be moved to the internal
** node to replace the deleted cell. */
if( !pPage->leaf ){
MemPage *pLeaf = pCur->pPage;
int nCell;
Pgno n;
unsigned char *pTmp;
if( pLeaf->nFree<0 ){
rc = btreeComputeFreeSpace(pLeaf);
if( rc ) return rc;
}
if( iCellDepth<pCur->iPage-1 ){
n = pCur->apPage[iCellDepth+1]->pgno;
}else{
n = pCur->pPage->pgno;
}
pCell = findCell(pLeaf, pLeaf->nCell-1);
if( pCell<&pLeaf->aData[4] ) return SQLITE_CORRUPT_BKPT;
nCell = pLeaf->xCellSize(pLeaf, pCell);
assert( MX_CELL_SIZE(pBt) >= nCell );
pTmp = pBt->pTmpSpace;
assert( pTmp!=0 );
rc = sqlite3PagerWrite(pLeaf->pDbPage);
if( rc==SQLITE_OK ){
insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n, &rc);
}
dropCell(pLeaf, pLeaf->nCell-1, nCell, &rc);
if( rc ) return rc;
}
/* Balance the tree. If the entry deleted was located on a leaf page,
** then the cursor still points to that page. In this case the first
** call to balance() repairs the tree, and the if(...) condition is
** never true.
**
** Otherwise, if the entry deleted was on an internal node page, then
** pCur is pointing to the leaf page from which a cell was removed to
** replace the cell deleted from the internal node. This is slightly
** tricky as the leaf node may be underfull, and the internal node may
** be either under or overfull. In this case run the balancing algorithm
** on the leaf node first. If the balance proceeds far enough up the
** tree that we can be sure that any problem in the internal node has
** been corrected, so be it. Otherwise, after balancing the leaf node,
** walk the cursor up the tree to the internal node and balance it as
** well. */
rc = balance(pCur);
if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
releasePageNotNull(pCur->pPage);
pCur->iPage--;
while( pCur->iPage>iCellDepth ){
releasePage(pCur->apPage[pCur->iPage--]);
}
pCur->pPage = pCur->apPage[pCur->iPage];
rc = balance(pCur);
}
if( rc==SQLITE_OK ){
if( bSkipnext ){
assert( bPreserve && (pCur->iPage==iCellDepth || CORRUPT_DB) );
assert( pPage==pCur->pPage || CORRUPT_DB );
assert( (pPage->nCell>0 || CORRUPT_DB) && iCellIdx<=pPage->nCell );
pCur->eState = CURSOR_SKIPNEXT;
if( iCellIdx>=pPage->nCell ){
pCur->skipNext = -1;
pCur->ix = pPage->nCell-1;
}else{
pCur->skipNext = 1;
}
}else{
rc = moveToRoot(pCur);
if( bPreserve ){
btreeReleaseAllCursorPages(pCur);
pCur->eState = CURSOR_REQUIRESEEK;
}
if( rc==SQLITE_EMPTY ) rc = SQLITE_OK;
}
}
return rc;
}
/*
** Create a new BTree table. Write into *piTable the page
** number for the root page of the new table.
**
** The type of type is determined by the flags parameter. Only the
** following values of flags are currently in use. Other values for
** flags might not work:
**
** BTREE_INTKEY|BTREE_LEAFDATA Used for SQL tables with rowid keys
** BTREE_ZERODATA Used for SQL indices
*/
static int btreeCreateTable(Btree *p, Pgno *piTable, int createTabFlags){
BtShared *pBt = p->pBt;
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
int ptfFlags; /* Page-type flage for the root page of new table */
assert( sqlite3BtreeHoldsMutex(p) );
assert( pBt->inTransaction==TRANS_WRITE );
assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ){
return rc;
}
#else
if( pBt->autoVacuum ){
Pgno pgnoMove; /* Move a page here to make room for the root-page */
MemPage *pPageMove; /* The page to move to. */
/* Creating a new table may probably require moving an existing database
** to make room for the new tables root page. In case this page turns
** out to be an overflow page, delete all overflow page-map caches
** held by open cursors.
*/
invalidateAllOverflowCache(pBt);
/* Read the value of meta[3] from the database to determine where the
** root page of the new table should go. meta[3] is the largest root-page
** created so far, so the new root-page is (meta[3]+1).
*/
sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
if( pgnoRoot>btreePagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
pgnoRoot++;
/* The new root-page may not be allocated on a pointer-map page, or the
** PENDING_BYTE page.
*/
while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
pgnoRoot++;
}
assert( pgnoRoot>=3 );
/* Allocate a page. The page that currently resides at pgnoRoot will
** be moved to the allocated page (unless the allocated page happens
** to reside at pgnoRoot).
*/
rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, BTALLOC_EXACT);
if( rc!=SQLITE_OK ){
return rc;
}
if( pgnoMove!=pgnoRoot ){
/* pgnoRoot is the page that will be used for the root-page of
** the new table (assuming an error did not occur). But we were
** allocated pgnoMove. If required (i.e. if it was not allocated
** by extending the file), the current page at position pgnoMove
** is already journaled.
*/
u8 eType = 0;
Pgno iPtrPage = 0;
/* Save the positions of any open cursors. This is required in
** case they are holding a reference to an xFetch reference
** corresponding to page pgnoRoot. */
rc = saveAllCursors(pBt, 0, 0);
releasePage(pPageMove);
if( rc!=SQLITE_OK ){
return rc;
}
/* Move the page currently at pgnoRoot to pgnoMove. */
rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
if( eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
rc = SQLITE_CORRUPT_BKPT;
}
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
assert( eType!=PTRMAP_ROOTPAGE );
assert( eType!=PTRMAP_FREEPAGE );
rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
releasePage(pRoot);
/* Obtain the page at pgnoRoot */
if( rc!=SQLITE_OK ){
return rc;
}
rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
}else{
pRoot = pPageMove;
}
/* Update the pointer-map and meta-data with the new root-page number. */
ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0, &rc);
if( rc ){
releasePage(pRoot);
return rc;
}
/* When the new root page was allocated, page 1 was made writable in
** order either to increase the database filesize, or to decrement the
** freelist count. Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
*/
assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
if( NEVER(rc) ){
releasePage(pRoot);
return rc;
}
}else{
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ) return rc;
}
#endif
assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
if( createTabFlags & BTREE_INTKEY ){
ptfFlags = PTF_INTKEY | PTF_LEAFDATA | PTF_LEAF;
}else{
ptfFlags = PTF_ZERODATA | PTF_LEAF;
}
zeroPage(pRoot, ptfFlags);
sqlite3PagerUnref(pRoot->pDbPage);
assert( (pBt->openFlags & BTREE_SINGLE)==0 || pgnoRoot==2 );
*piTable = pgnoRoot;
return SQLITE_OK;
}
int sqlite3BtreeCreateTable(Btree *p, Pgno *piTable, int flags){
int rc;
sqlite3BtreeEnter(p);
rc = btreeCreateTable(p, piTable, flags);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Erase the given database page and all its children. Return
** the page to the freelist.
*/
static int clearDatabasePage(
BtShared *pBt, /* The BTree that contains the table */
Pgno pgno, /* Page number to clear */
int freePageFlag, /* Deallocate page if true */
int *pnChange /* Add number of Cells freed to this counter */
){
MemPage *pPage;
int rc;
unsigned char *pCell;
int i;
int hdr;
CellInfo info;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno>btreePagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getAndInitPage(pBt, pgno, &pPage, 0, 0);
if( rc ) return rc;
if( pPage->bBusy ){
rc = SQLITE_CORRUPT_BKPT;
goto cleardatabasepage_out;
}
pPage->bBusy = 1;
hdr = pPage->hdrOffset;
for(i=0; i<pPage->nCell; i++){
pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
if( rc ) goto cleardatabasepage_out;
}
rc = clearCell(pPage, pCell, &info);
if( rc ) goto cleardatabasepage_out;
}
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pPage->aData[hdr+8]), 1, pnChange);
if( rc ) goto cleardatabasepage_out;
}else if( pnChange ){
assert( pPage->intKey || CORRUPT_DB );
testcase( !pPage->intKey );
*pnChange += pPage->nCell;
}
if( freePageFlag ){
freePage(pPage, &rc);
}else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
zeroPage(pPage, pPage->aData[hdr] | PTF_LEAF);
}
cleardatabasepage_out:
pPage->bBusy = 0;
releasePage(pPage);
return rc;
}
/*
** Delete all information from a single table in the database. iTable is
** the page number of the root of the table. After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table. Open write cursors are moved to the
** root of the table.
**
** If pnChange is not NULL, then table iTable must be an intkey table. The
** integer value pointed to by pnChange is incremented by the number of
** entries in the table.
*/
int sqlite3BtreeClearTable(Btree *p, int iTable, int *pnChange){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( p->inTrans==TRANS_WRITE );
rc = saveAllCursors(pBt, (Pgno)iTable, 0);
if( SQLITE_OK==rc ){
/* Invalidate all incrblob cursors open on table iTable (assuming iTable
** is the root of a table b-tree - if it is not, the following call is
** a no-op). */
invalidateIncrblobCursors(p, (Pgno)iTable, 0, 1);
rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Delete all information from the single table that pCur is open on.
**
** This routine only work for pCur on an ephemeral table.
*/
int sqlite3BtreeClearTableOfCursor(BtCursor *pCur){
return sqlite3BtreeClearTable(pCur->pBtree, pCur->pgnoRoot, 0);
}
/*
** Erase all information in a table and add the root of the table to
** the freelist. Except, the root of the principle table (the one on
** page 1) is never added to the freelist.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** cursors on the table.
**
** If AUTOVACUUM is enabled and the page at iTable is not the last
** root page in the database file, then the last root page
** in the database file is moved into the slot formerly occupied by
** iTable and that last slot formerly occupied by the last root page
** is added to the freelist instead of iTable. In this say, all
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right. *piMoved is set to the
** page number that used to be the last root page in the file before
** the move. If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
int rc;
MemPage *pPage = 0;
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->inTrans==TRANS_WRITE );
assert( iTable>=2 );
if( iTable>btreePagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
if( rc ) return rc;
rc = sqlite3BtreeClearTable(p, iTable, 0);
if( rc ){
releasePage(pPage);
return rc;
}
*piMoved = 0;
#ifdef SQLITE_OMIT_AUTOVACUUM
freePage(pPage, &rc);
releasePage(pPage);
#else
if( pBt->autoVacuum ){
Pgno maxRootPgno;
sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
if( iTable==maxRootPgno ){
/* If the table being dropped is the table with the largest root-page
** number in the database, put the root page on the free list.
*/
freePage(pPage, &rc);
releasePage(pPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
/* The table being dropped does not have the largest root-page
** number in the database. So move the page that does into the
** gap left by the deleted root-page.
*/
MemPage *pMove;
releasePage(pPage);
rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
pMove = 0;
rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
freePage(pMove, &rc);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
*piMoved = maxRootPgno;
}
/* Set the new 'max-root-page' value in the database header. This
** is the old value less one, less one more if that happens to
** be a root-page number, less one again if that is the
** PENDING_BYTE_PAGE.
*/
maxRootPgno--;
while( maxRootPgno==PENDING_BYTE_PAGE(pBt)
|| PTRMAP_ISPAGE(pBt, maxRootPgno) ){
maxRootPgno--;
}
assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
}else{
freePage(pPage, &rc);
releasePage(pPage);
}
#endif
return rc;
}
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
int rc;
sqlite3BtreeEnter(p);
rc = btreeDropTable(p, iTable, piMoved);
sqlite3BtreeLeave(p);
return rc;
}
/*
** This function may only be called if the b-tree connection already
** has a read or write transaction open on the database.
**
** Read the meta-information out of a database file. Meta[0]
** is the number of free pages currently in the database. Meta[1]
** through meta[15] are available for use by higher layers. Meta[0]
** is read-only, the others are read/write.
**
** The schema layer numbers meta values differently. At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible. So Cookie[0] is the same as Meta[1].
**
** This routine treats Meta[BTREE_DATA_VERSION] as a special case. Instead
** of reading the value out of the header, it instead loads the "DataVersion"
** from the pager. The BTREE_DATA_VERSION value is not actually stored in the
** database file. It is a number computed by the pager. But its access
** pattern is the same as header meta values, and so it is convenient to
** read it from this routine.
*/
void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( p->inTrans>TRANS_NONE );
assert( SQLITE_OK==querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK) );
assert( pBt->pPage1 );
assert( idx>=0 && idx<=15 );
if( idx==BTREE_DATA_VERSION ){
*pMeta = sqlite3PagerDataVersion(pBt->pPager) + p->iBDataVersion;
}else{
*pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
}
/* If auto-vacuum is disabled in this build and this is an auto-vacuum
** database, mark the database as read-only. */
#ifdef SQLITE_OMIT_AUTOVACUUM
if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ){
pBt->btsFlags |= BTS_READ_ONLY;
}
#endif
sqlite3BtreeLeave(p);
}
/*
** Write meta-information back into the database. Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
BtShared *pBt = p->pBt;
unsigned char *pP1;
int rc;
assert( idx>=1 && idx<=15 );
sqlite3BtreeEnter(p);
assert( p->inTrans==TRANS_WRITE );
assert( pBt->pPage1!=0 );
pP1 = pBt->pPage1->aData;
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pP1[36 + idx*4], iMeta);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( idx==BTREE_INCR_VACUUM ){
assert( pBt->autoVacuum || iMeta==0 );
assert( iMeta==0 || iMeta==1 );
pBt->incrVacuum = (u8)iMeta;
}
#endif
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** The first argument, pCur, is a cursor opened on some b-tree. Count the
** number of entries in the b-tree and write the result to *pnEntry.
**
** SQLITE_OK is returned if the operation is successfully executed.
** Otherwise, if an error is encountered (i.e. an IO error or database
** corruption) an SQLite error code is returned.
*/
int sqlite3BtreeCount(sqlite3 *db, BtCursor *pCur, i64 *pnEntry){
i64 nEntry = 0; /* Value to return in *pnEntry */
int rc; /* Return code */
rc = moveToRoot(pCur);
if( rc==SQLITE_EMPTY ){
*pnEntry = 0;
return SQLITE_OK;
}
/* Unless an error occurs, the following loop runs one iteration for each
** page in the B-Tree structure (not including overflow pages).
*/
while( rc==SQLITE_OK && !AtomicLoad(&db->u1.isInterrupted) ){
int iIdx; /* Index of child node in parent */
MemPage *pPage; /* Current page of the b-tree */
/* If this is a leaf page or the tree is not an int-key tree, then
** this page contains countable entries. Increment the entry counter
** accordingly.
*/
pPage = pCur->pPage;
if( pPage->leaf || !pPage->intKey ){
nEntry += pPage->nCell;
}
/* pPage is a leaf node. This loop navigates the cursor so that it
** points to the first interior cell that it points to the parent of
** the next page in the tree that has not yet been visited. The
** pCur->aiIdx[pCur->iPage] value is set to the index of the parent cell
** of the page, or to the number of cells in the page if the next page
** to visit is the right-child of its parent.
**
** If all pages in the tree have been visited, return SQLITE_OK to the
** caller.
*/
if( pPage->leaf ){
do {
if( pCur->iPage==0 ){
/* All pages of the b-tree have been visited. Return successfully. */
*pnEntry = nEntry;
return moveToRoot(pCur);
}
moveToParent(pCur);
}while ( pCur->ix>=pCur->pPage->nCell );
pCur->ix++;
pPage = pCur->pPage;
}
/* Descend to the child node of the cell that the cursor currently
** points at. This is the right-child if (iIdx==pPage->nCell).
*/
iIdx = pCur->ix;
if( iIdx==pPage->nCell ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
}else{
rc = moveToChild(pCur, get4byte(findCell(pPage, iIdx)));
}
}
/* An error has occurred. Return an error code. */
return rc;
}
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
return p->pBt->pPager;
}
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
IntegrityCk *pCheck,
const char *zFormat,
...
){
va_list ap;
if( !pCheck->mxErr ) return;
pCheck->mxErr--;
pCheck->nErr++;
va_start(ap, zFormat);
if( pCheck->errMsg.nChar ){
sqlite3_str_append(&pCheck->errMsg, "\n", 1);
}
if( pCheck->zPfx ){
sqlite3_str_appendf(&pCheck->errMsg, pCheck->zPfx, pCheck->v1, pCheck->v2);
}
sqlite3_str_vappendf(&pCheck->errMsg, zFormat, ap);
va_end(ap);
if( pCheck->errMsg.accError==SQLITE_NOMEM ){
pCheck->bOomFault = 1;
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Return non-zero if the bit in the IntegrityCk.aPgRef[] array that
** corresponds to page iPg is already set.
*/
static int getPageReferenced(IntegrityCk *pCheck, Pgno iPg){
assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
return (pCheck->aPgRef[iPg/8] & (1 << (iPg & 0x07)));
}
/*
** Set the bit in the IntegrityCk.aPgRef[] array that corresponds to page iPg.
*/
static void setPageReferenced(IntegrityCk *pCheck, Pgno iPg){
assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
pCheck->aPgRef[iPg/8] |= (1 << (iPg & 0x07));
}
/*
** Add 1 to the reference count for page iPage. If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 or more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, Pgno iPage){
if( iPage>pCheck->nPage || iPage==0 ){
checkAppendMsg(pCheck, "invalid page number %d", iPage);
return 1;
}
if( getPageReferenced(pCheck, iPage) ){
checkAppendMsg(pCheck, "2nd reference to page %d", iPage);
return 1;
}
if( AtomicLoad(&pCheck->db->u1.isInterrupted) ) return 1;
setPageReferenced(pCheck, iPage);
return 0;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Check that the entry in the pointer-map for page iChild maps to
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
IntegrityCk *pCheck, /* Integrity check context */
Pgno iChild, /* Child page number */
u8 eType, /* Expected pointer map type */
Pgno iParent /* Expected pointer map parent page number */
){
int rc;
u8 ePtrmapType;
Pgno iPtrmapParent;
rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->bOomFault = 1;
checkAppendMsg(pCheck, "Failed to read ptrmap key=%d", iChild);
return;
}
if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
checkAppendMsg(pCheck,
"Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)",
iChild, eType, iParent, ePtrmapType, iPtrmapParent);
}
}
#endif
/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
IntegrityCk *pCheck, /* Integrity checking context */
int isFreeList, /* True for a freelist. False for overflow page list */
Pgno iPage, /* Page number for first page in the list */
u32 N /* Expected number of pages in the list */
){
int i;
u32 expected = N;
int nErrAtStart = pCheck->nErr;
while( iPage!=0 && pCheck->mxErr ){
DbPage *pOvflPage;
unsigned char *pOvflData;
if( checkRef(pCheck, iPage) ) break;
N--;
if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage, 0) ){
checkAppendMsg(pCheck, "failed to get page %d", iPage);
break;
}
pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
if( isFreeList ){
u32 n = (u32)get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0);
}
#endif
if( n>pCheck->pBt->usableSize/4-2 ){
checkAppendMsg(pCheck,
"freelist leaf count too big on page %d", iPage);
N--;
}else{
for(i=0; i<(int)n; i++){
Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0);
}
#endif
checkRef(pCheck, iFreePage);
}
N -= n;
}
}
#ifndef SQLITE_OMIT_AUTOVACUUM
else{
/* If this database supports auto-vacuum and iPage is not the last
** page in this overflow list, check that the pointer-map entry for
** the following page matches iPage.
*/
if( pCheck->pBt->autoVacuum && N>0 ){
i = get4byte(pOvflData);
checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage);
}
}
#endif
iPage = get4byte(pOvflData);
sqlite3PagerUnref(pOvflPage);
}
if( N && nErrAtStart==pCheck->nErr ){
checkAppendMsg(pCheck,
"%s is %d but should be %d",
isFreeList ? "size" : "overflow list length",
expected-N, expected);
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** An implementation of a min-heap.
**
** aHeap[0] is the number of elements on the heap. aHeap[1] is the
** root element. The daughter nodes of aHeap[N] are aHeap[N*2]
** and aHeap[N*2+1].
**
** The heap property is this: Every node is less than or equal to both
** of its daughter nodes. A consequence of the heap property is that the
** root node aHeap[1] is always the minimum value currently in the heap.
**
** The btreeHeapInsert() routine inserts an unsigned 32-bit number onto
** the heap, preserving the heap property. The btreeHeapPull() routine
** removes the root element from the heap (the minimum value in the heap)
** and then moves other nodes around as necessary to preserve the heap
** property.
**
** This heap is used for cell overlap and coverage testing. Each u32
** entry represents the span of a cell or freeblock on a btree page.
** The upper 16 bits are the index of the first byte of a range and the
** lower 16 bits are the index of the last byte of that range.
*/
static void btreeHeapInsert(u32 *aHeap, u32 x){
u32 j, i = ++aHeap[0];
aHeap[i] = x;
while( (j = i/2)>0 && aHeap[j]>aHeap[i] ){
x = aHeap[j];
aHeap[j] = aHeap[i];
aHeap[i] = x;
i = j;
}
}
static int btreeHeapPull(u32 *aHeap, u32 *pOut){
u32 j, i, x;
if( (x = aHeap[0])==0 ) return 0;
*pOut = aHeap[1];
aHeap[1] = aHeap[x];
aHeap[x] = 0xffffffff;
aHeap[0]--;
i = 1;
while( (j = i*2)<=aHeap[0] ){
if( aHeap[j]>aHeap[j+1] ) j++;
if( aHeap[i]<aHeap[j] ) break;
x = aHeap[i];
aHeap[i] = aHeap[j];
aHeap[j] = x;
i = j;
}
return 1;
}
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Do various sanity checks on a single page of a tree. Return
** the tree depth. Root pages return 0. Parents of root pages
** return 1, and so forth.
**
** These checks are done:
**
** 1. Make sure that cells and freeblocks do not overlap
** but combine to completely cover the page.
** 2. Make sure integer cell keys are in order.
** 3. Check the integrity of overflow pages.
** 4. Recursively call checkTreePage on all children.
** 5. Verify that the depth of all children is the same.
*/
static int checkTreePage(
IntegrityCk *pCheck, /* Context for the sanity check */
Pgno iPage, /* Page number of the page to check */
i64 *piMinKey, /* Write minimum integer primary key here */
i64 maxKey /* Error if integer primary key greater than this */
){
MemPage *pPage = 0; /* The page being analyzed */
int i; /* Loop counter */
int rc; /* Result code from subroutine call */
int depth = -1, d2; /* Depth of a subtree */
int pgno; /* Page number */
int nFrag; /* Number of fragmented bytes on the page */
int hdr; /* Offset to the page header */
int cellStart; /* Offset to the start of the cell pointer array */
int nCell; /* Number of cells */
int doCoverageCheck = 1; /* True if cell coverage checking should be done */
int keyCanBeEqual = 1; /* True if IPK can be equal to maxKey
** False if IPK must be strictly less than maxKey */
u8 *data; /* Page content */
u8 *pCell; /* Cell content */
u8 *pCellIdx; /* Next element of the cell pointer array */
BtShared *pBt; /* The BtShared object that owns pPage */
u32 pc; /* Address of a cell */
u32 usableSize; /* Usable size of the page */
u32 contentOffset; /* Offset to the start of the cell content area */
u32 *heap = 0; /* Min-heap used for checking cell coverage */
u32 x, prev = 0; /* Next and previous entry on the min-heap */
const char *saved_zPfx = pCheck->zPfx;
int saved_v1 = pCheck->v1;
int saved_v2 = pCheck->v2;
u8 savedIsInit = 0;
/* Check that the page exists
*/
pBt = pCheck->pBt;
usableSize = pBt->usableSize;
if( iPage==0 ) return 0;
if( checkRef(pCheck, iPage) ) return 0;
pCheck->zPfx = "Page %u: ";
pCheck->v1 = iPage;
if( (rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0 ){
checkAppendMsg(pCheck,
"unable to get the page. error code=%d", rc);
goto end_of_check;
}
/* Clear MemPage.isInit to make sure the corruption detection code in
** btreeInitPage() is executed. */
savedIsInit = pPage->isInit;
pPage->isInit = 0;
if( (rc = btreeInitPage(pPage))!=0 ){
assert( rc==SQLITE_CORRUPT ); /* The only possible error from InitPage */
checkAppendMsg(pCheck,
"btreeInitPage() returns error code %d", rc);
goto end_of_check;
}
if( (rc = btreeComputeFreeSpace(pPage))!=0 ){
assert( rc==SQLITE_CORRUPT );
checkAppendMsg(pCheck, "free space corruption", rc);
goto end_of_check;
}
data = pPage->aData;
hdr = pPage->hdrOffset;
/* Set up for cell analysis */
pCheck->zPfx = "On tree page %u cell %d: ";
contentOffset = get2byteNotZero(&data[hdr+5]);
assert( contentOffset<=usableSize ); /* Enforced by btreeInitPage() */
/* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
** number of cells on the page. */
nCell = get2byte(&data[hdr+3]);
assert( pPage->nCell==nCell );
/* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
** immediately follows the b-tree page header. */
cellStart = hdr + 12 - 4*pPage->leaf;
assert( pPage->aCellIdx==&data[cellStart] );
pCellIdx = &data[cellStart + 2*(nCell-1)];
if( !pPage->leaf ){
/* Analyze the right-child page of internal pages */
pgno = get4byte(&data[hdr+8]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
pCheck->zPfx = "On page %u at right child: ";
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
}
#endif
depth = checkTreePage(pCheck, pgno, &maxKey, maxKey);
keyCanBeEqual = 0;
}else{
/* For leaf pages, the coverage check will occur in the same loop
** as the other cell checks, so initialize the heap. */
heap = pCheck->heap;
heap[0] = 0;
}
/* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
** integer offsets to the cell contents. */
for(i=nCell-1; i>=0 && pCheck->mxErr; i--){
CellInfo info;
/* Check cell size */
pCheck->v2 = i;
assert( pCellIdx==&data[cellStart + i*2] );
pc = get2byteAligned(pCellIdx);
pCellIdx -= 2;
if( pc<contentOffset || pc>usableSize-4 ){
checkAppendMsg(pCheck, "Offset %d out of range %d..%d",
pc, contentOffset, usableSize-4);
doCoverageCheck = 0;
continue;
}
pCell = &data[pc];
pPage->xParseCell(pPage, pCell, &info);
if( pc+info.nSize>usableSize ){
checkAppendMsg(pCheck, "Extends off end of page");
doCoverageCheck = 0;
continue;
}
/* Check for integer primary key out of range */
if( pPage->intKey ){
if( keyCanBeEqual ? (info.nKey > maxKey) : (info.nKey >= maxKey) ){
checkAppendMsg(pCheck, "Rowid %lld out of order", info.nKey);
}
maxKey = info.nKey;
keyCanBeEqual = 0; /* Only the first key on the page may ==maxKey */
}
/* Check the content overflow list */
if( info.nPayload>info.nLocal ){
u32 nPage; /* Number of pages on the overflow chain */
Pgno pgnoOvfl; /* First page of the overflow chain */
assert( pc + info.nSize - 4 <= usableSize );
nPage = (info.nPayload - info.nLocal + usableSize - 5)/(usableSize - 4);
pgnoOvfl = get4byte(&pCell[info.nSize - 4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
}
#endif
checkList(pCheck, 0, pgnoOvfl, nPage);
}
if( !pPage->leaf ){
/* Check sanity of left child page for internal pages */
pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
}
#endif
d2 = checkTreePage(pCheck, pgno, &maxKey, maxKey);
keyCanBeEqual = 0;
if( d2!=depth ){
checkAppendMsg(pCheck, "Child page depth differs");
depth = d2;
}
}else{
/* Populate the coverage-checking heap for leaf pages */
btreeHeapInsert(heap, (pc<<16)|(pc+info.nSize-1));
}
}
*piMinKey = maxKey;
/* Check for complete coverage of the page
*/
pCheck->zPfx = 0;
if( doCoverageCheck && pCheck->mxErr>0 ){
/* For leaf pages, the min-heap has already been initialized and the
** cells have already been inserted. But for internal pages, that has
** not yet been done, so do it now */
if( !pPage->leaf ){
heap = pCheck->heap;
heap[0] = 0;
for(i=nCell-1; i>=0; i--){
u32 size;
pc = get2byteAligned(&data[cellStart+i*2]);
size = pPage->xCellSize(pPage, &data[pc]);
btreeHeapInsert(heap, (pc<<16)|(pc+size-1));
}
}
/* Add the freeblocks to the min-heap
**
** EVIDENCE-OF: R-20690-50594 The second field of the b-tree page header
** is the offset of the first freeblock, or zero if there are no
** freeblocks on the page.
*/
i = get2byte(&data[hdr+1]);
while( i>0 ){
int size, j;
assert( (u32)i<=usableSize-4 ); /* Enforced by btreeComputeFreeSpace() */
size = get2byte(&data[i+2]);
assert( (u32)(i+size)<=usableSize ); /* due to btreeComputeFreeSpace() */
btreeHeapInsert(heap, (((u32)i)<<16)|(i+size-1));
/* EVIDENCE-OF: R-58208-19414 The first 2 bytes of a freeblock are a
** big-endian integer which is the offset in the b-tree page of the next
** freeblock in the chain, or zero if the freeblock is the last on the
** chain. */
j = get2byte(&data[i]);
/* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
** increasing offset. */
assert( j==0 || j>i+size ); /* Enforced by btreeComputeFreeSpace() */
assert( (u32)j<=usableSize-4 ); /* Enforced by btreeComputeFreeSpace() */
i = j;
}
/* Analyze the min-heap looking for overlap between cells and/or
** freeblocks, and counting the number of untracked bytes in nFrag.
**
** Each min-heap entry is of the form: (start_address<<16)|end_address.
** There is an implied first entry the covers the page header, the cell
** pointer index, and the gap between the cell pointer index and the start
** of cell content.
**
** The loop below pulls entries from the min-heap in order and compares
** the start_address against the previous end_address. If there is an
** overlap, that means bytes are used multiple times. If there is a gap,
** that gap is added to the fragmentation count.
*/
nFrag = 0;
prev = contentOffset - 1; /* Implied first min-heap entry */
while( btreeHeapPull(heap,&x) ){
if( (prev&0xffff)>=(x>>16) ){
checkAppendMsg(pCheck,
"Multiple uses for byte %u of page %u", x>>16, iPage);
break;
}else{
nFrag += (x>>16) - (prev&0xffff) - 1;
prev = x;
}
}
nFrag += usableSize - (prev&0xffff) - 1;
/* EVIDENCE-OF: R-43263-13491 The total number of bytes in all fragments
** is stored in the fifth field of the b-tree page header.
** EVIDENCE-OF: R-07161-27322 The one-byte integer at offset 7 gives the
** number of fragmented free bytes within the cell content area.
*/
if( heap[0]==0 && nFrag!=data[hdr+7] ){
checkAppendMsg(pCheck,
"Fragmentation of %d bytes reported as %d on page %u",
nFrag, data[hdr+7], iPage);
}
}
end_of_check:
if( !doCoverageCheck ) pPage->isInit = savedIsInit;
releasePage(pPage);
pCheck->zPfx = saved_zPfx;
pCheck->v1 = saved_v1;
pCheck->v2 = saved_v2;
return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file. aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table. nRoot is the number of entries in aRoot.
**
** A read-only or read-write transaction must be opened before calling
** this function.
**
** Write the number of error seen in *pnErr. Except for some memory
** allocation errors, an error message held in memory obtained from
** malloc is returned if *pnErr is non-zero. If *pnErr==0 then NULL is
** returned. If a memory allocation error occurs, NULL is returned.
**
** If the first entry in aRoot[] is 0, that indicates that the list of
** root pages is incomplete. This is a "partial integrity-check". This
** happens when performing an integrity check on a single table. The
** zero is skipped, of course. But in addition, the freelist checks
** and the checks to make sure every page is referenced are also skipped,
** since obviously it is not possible to know which pages are covered by
** the unverified btrees. Except, if aRoot[1] is 1, then the freelist
** checks are still performed.
*/
char *sqlite3BtreeIntegrityCheck(
sqlite3 *db, /* Database connection that is running the check */
Btree *p, /* The btree to be checked */
Pgno *aRoot, /* An array of root pages numbers for individual trees */
int nRoot, /* Number of entries in aRoot[] */
int mxErr, /* Stop reporting errors after this many */
int *pnErr /* Write number of errors seen to this variable */
){
Pgno i;
IntegrityCk sCheck;
BtShared *pBt = p->pBt;
u64 savedDbFlags = pBt->db->flags;
char zErr[100];
int bPartial = 0; /* True if not checking all btrees */
int bCkFreelist = 1; /* True to scan the freelist */
VVA_ONLY( int nRef );
assert( nRoot>0 );
/* aRoot[0]==0 means this is a partial check */
if( aRoot[0]==0 ){
assert( nRoot>1 );
bPartial = 1;
if( aRoot[1]!=1 ) bCkFreelist = 0;
}
sqlite3BtreeEnter(p);
assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
VVA_ONLY( nRef = sqlite3PagerRefcount(pBt->pPager) );
assert( nRef>=0 );
sCheck.db = db;
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = btreePagecount(sCheck.pBt);
sCheck.mxErr = mxErr;
sCheck.nErr = 0;
sCheck.bOomFault = 0;
sCheck.zPfx = 0;
sCheck.v1 = 0;
sCheck.v2 = 0;
sCheck.aPgRef = 0;
sCheck.heap = 0;
sqlite3StrAccumInit(&sCheck.errMsg, 0, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
sCheck.errMsg.printfFlags = SQLITE_PRINTF_INTERNAL;
if( sCheck.nPage==0 ){
goto integrity_ck_cleanup;
}
sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
if( !sCheck.aPgRef ){
sCheck.bOomFault = 1;
goto integrity_ck_cleanup;
}
sCheck.heap = (u32*)sqlite3PageMalloc( pBt->pageSize );
if( sCheck.heap==0 ){
sCheck.bOomFault = 1;
goto integrity_ck_cleanup;
}
i = PENDING_BYTE_PAGE(pBt);
if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
/* Check the integrity of the freelist
*/
if( bCkFreelist ){
sCheck.zPfx = "Main freelist: ";
checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
get4byte(&pBt->pPage1->aData[36]));
sCheck.zPfx = 0;
}
/* Check all the tables.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
if( !bPartial ){
if( pBt->autoVacuum ){
Pgno mx = 0;
Pgno mxInHdr;
for(i=0; (int)i<nRoot; i++) if( mx<aRoot[i] ) mx = aRoot[i];
mxInHdr = get4byte(&pBt->pPage1->aData[52]);
if( mx!=mxInHdr ){
checkAppendMsg(&sCheck,
"max rootpage (%d) disagrees with header (%d)",
mx, mxInHdr
);
}
}else if( get4byte(&pBt->pPage1->aData[64])!=0 ){
checkAppendMsg(&sCheck,
"incremental_vacuum enabled with a max rootpage of zero"
);
}
}
#endif
testcase( pBt->db->flags & SQLITE_CellSizeCk );
pBt->db->flags &= ~(u64)SQLITE_CellSizeCk;
for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
i64 notUsed;
if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && aRoot[i]>1 && !bPartial ){
checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0);
}
#endif
checkTreePage(&sCheck, aRoot[i], &notUsed, LARGEST_INT64);
}
pBt->db->flags = savedDbFlags;
/* Make sure every page in the file is referenced
*/
if( !bPartial ){
for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
if( getPageReferenced(&sCheck, i)==0 ){
checkAppendMsg(&sCheck, "Page %d is never used", i);
}
#else
/* If the database supports auto-vacuum, make sure no tables contain
** references to pointer-map pages.
*/
if( getPageReferenced(&sCheck, i)==0 &&
(PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
checkAppendMsg(&sCheck, "Page %d is never used", i);
}
if( getPageReferenced(&sCheck, i)!=0 &&
(PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
checkAppendMsg(&sCheck, "Pointer map page %d is referenced", i);
}
#endif
}
}
/* Clean up and report errors.
*/
integrity_ck_cleanup:
sqlite3PageFree(sCheck.heap);
sqlite3_free(sCheck.aPgRef);
if( sCheck.bOomFault ){
sqlite3_str_reset(&sCheck.errMsg);
sCheck.nErr++;
}
*pnErr = sCheck.nErr;
if( sCheck.nErr==0 ) sqlite3_str_reset(&sCheck.errMsg);
/* Make sure this analysis did not leave any unref() pages. */
assert( nRef==sqlite3PagerRefcount(pBt->pPager) );
sqlite3BtreeLeave(p);
return sqlite3StrAccumFinish(&sCheck.errMsg);
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** Return the full pathname of the underlying database file. Return
** an empty string if the database is in-memory or a TEMP database.
**
** The pager filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerFilename(p->pBt->pPager, 1);
}
/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
**
** The pager journal filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetJournalname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerJournalname(p->pBt->pPager);
}
/*
** Return one of SQLITE_TXN_NONE, SQLITE_TXN_READ, or SQLITE_TXN_WRITE
** to describe the current transaction state of Btree p.
*/
int sqlite3BtreeTxnState(Btree *p){
assert( p==0 || sqlite3_mutex_held(p->db->mutex) );
return p ? p->inTrans : 0;
}
#ifndef SQLITE_OMIT_WAL
/*
** Run a checkpoint on the Btree passed as the first argument.
**
** Return SQLITE_LOCKED if this or any other connection has an open
** transaction on the shared-cache the argument Btree is connected to.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite3BtreeCheckpoint(Btree *p, int eMode, int *pnLog, int *pnCkpt){
int rc = SQLITE_OK;
if( p ){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( pBt->inTransaction!=TRANS_NONE ){
rc = SQLITE_LOCKED;
}else{
rc = sqlite3PagerCheckpoint(pBt->pPager, p->db, eMode, pnLog, pnCkpt);
}
sqlite3BtreeLeave(p);
}
return rc;
}
#endif
/*
** Return true if there is currently a backup running on Btree p.
*/
int sqlite3BtreeIsInBackup(Btree *p){
assert( p );
assert( sqlite3_mutex_held(p->db->mutex) );
return p->nBackup!=0;
}
/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for its own
** purposes (for example, to store a high-level schema associated with
** the shared-btree). The btree layer manages reference counting issues.
**
** The first time this is called on a shared-btree, nBytes bytes of memory
** are allocated, zeroed, and returned to the caller. For each subsequent
** call the nBytes parameter is ignored and a pointer to the same blob
** of memory returned.
**
** If the nBytes parameter is 0 and the blob of memory has not yet been
** allocated, a null pointer is returned. If the blob has already been
** allocated, it is returned as normal.
**
** Just before the shared-btree is closed, the function passed as the
** xFree argument when the memory allocation was made is invoked on the
** blob of allocated memory. The xFree function should not call sqlite3_free()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( !pBt->pSchema && nBytes ){
pBt->pSchema = sqlite3DbMallocZero(0, nBytes);
pBt->xFreeSchema = xFree;
}
sqlite3BtreeLeave(p);
return pBt->pSchema;
}
/*
** Return SQLITE_LOCKED_SHAREDCACHE if another user of the same shared
** btree as the argument handle holds an exclusive lock on the
** sqlite_schema table. Otherwise SQLITE_OK.
*/
int sqlite3BtreeSchemaLocked(Btree *p){
int rc;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
rc = querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK);
assert( rc==SQLITE_OK || rc==SQLITE_LOCKED_SHAREDCACHE );
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab. The
** lock is a write lock if isWritelock is true or a read lock
** if it is false.
*/
int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
int rc = SQLITE_OK;
assert( p->inTrans!=TRANS_NONE );
if( p->sharable ){
u8 lockType = READ_LOCK + isWriteLock;
assert( READ_LOCK+1==WRITE_LOCK );
assert( isWriteLock==0 || isWriteLock==1 );
sqlite3BtreeEnter(p);
rc = querySharedCacheTableLock(p, iTab, lockType);
if( rc==SQLITE_OK ){
rc = setSharedCacheTableLock(p, iTab, lockType);
}
sqlite3BtreeLeave(p);
}
return rc;
}
#endif
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Argument pCsr must be a cursor opened for writing on an
** INTKEY table currently pointing at a valid table entry.
** This function modifies the data stored as part of that entry.
**
** Only the data content may only be modified, it is not possible to
** change the length of the data stored. If this function is called with
** parameters that attempt to write past the end of the existing data,
** no modifications are made and SQLITE_CORRUPT is returned.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
int rc;
assert( cursorOwnsBtShared(pCsr) );
assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
assert( pCsr->curFlags & BTCF_Incrblob );
rc = restoreCursorPosition(pCsr);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pCsr->eState!=CURSOR_REQUIRESEEK );
if( pCsr->eState!=CURSOR_VALID ){
return SQLITE_ABORT;
}
/* Save the positions of all other cursors open on this table. This is
** required in case any of them are holding references to an xFetch
** version of the b-tree page modified by the accessPayload call below.
**
** Note that pCsr must be open on a INTKEY table and saveCursorPosition()
** and hence saveAllCursors() cannot fail on a BTREE_INTKEY table, hence
** saveAllCursors can only return SQLITE_OK.
*/
VVA_ONLY(rc =) saveAllCursors(pCsr->pBt, pCsr->pgnoRoot, pCsr);
assert( rc==SQLITE_OK );
/* Check some assumptions:
** (a) the cursor is open for writing,
** (b) there is a read/write transaction open,
** (c) the connection holds a write-lock on the table (if required),
** (d) there are no conflicting read-locks, and
** (e) the cursor points at a valid row of an intKey table.
*/
if( (pCsr->curFlags & BTCF_WriteFlag)==0 ){
return SQLITE_READONLY;
}
assert( (pCsr->pBt->btsFlags & BTS_READ_ONLY)==0
&& pCsr->pBt->inTransaction==TRANS_WRITE );
assert( hasSharedCacheTableLock(pCsr->pBtree, pCsr->pgnoRoot, 0, 2) );
assert( !hasReadConflicts(pCsr->pBtree, pCsr->pgnoRoot) );
assert( pCsr->pPage->intKey );
return accessPayload(pCsr, offset, amt, (unsigned char *)z, 1);
}
/*
** Mark this cursor as an incremental blob cursor.
*/
void sqlite3BtreeIncrblobCursor(BtCursor *pCur){
pCur->curFlags |= BTCF_Incrblob;
pCur->pBtree->hasIncrblobCur = 1;
}
#endif
/*
** Set both the "read version" (single byte at byte offset 18) and
** "write version" (single byte at byte offset 19) fields in the database
** header to iVersion.
*/
int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
BtShared *pBt = pBtree->pBt;
int rc; /* Return code */
assert( iVersion==1 || iVersion==2 );
/* If setting the version fields to 1, do not automatically open the
** WAL connection, even if the version fields are currently set to 2.
*/
pBt->btsFlags &= ~BTS_NO_WAL;
if( iVersion==1 ) pBt->btsFlags |= BTS_NO_WAL;
rc = sqlite3BtreeBeginTrans(pBtree, 0, 0);
if( rc==SQLITE_OK ){
u8 *aData = pBt->pPage1->aData;
if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
rc = sqlite3BtreeBeginTrans(pBtree, 2, 0);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc==SQLITE_OK ){
aData[18] = (u8)iVersion;
aData[19] = (u8)iVersion;
}
}
}
}
pBt->btsFlags &= ~BTS_NO_WAL;
return rc;
}
/*
** Return true if the cursor has a hint specified. This routine is
** only used from within assert() statements
*/
int sqlite3BtreeCursorHasHint(BtCursor *pCsr, unsigned int mask){
return (pCsr->hints & mask)!=0;
}
/*
** Return true if the given Btree is read-only.
*/
int sqlite3BtreeIsReadonly(Btree *p){
return (p->pBt->btsFlags & BTS_READ_ONLY)!=0;
}
/*
** Return the size of the header added to each page by this module.
*/
int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage)); }
#if !defined(SQLITE_OMIT_SHARED_CACHE)
/*
** Return true if the Btree passed as the only argument is sharable.
*/
int sqlite3BtreeSharable(Btree *p){
return p->sharable;
}
/*
** Return the number of connections to the BtShared object accessed by
** the Btree handle passed as the only argument. For private caches
** this is always 1. For shared caches it may be 1 or greater.
*/
int sqlite3BtreeConnectionCount(Btree *p){
testcase( p->sharable );
return p->pBt->nRef;
}
#endif
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