Move utility package 'graphdb' to pkg/graphdb

graphdb/MAINTAINERS

@@ -0,0 +1 @@
+Michael Crosby <michael@crosbymichael.com> (@crosbymichael)

graphdb/conn_darwin.go

@@ -0,0 +1,5 @@
+package graphdb
+
+func NewSqliteConn(root string) (*Database, error) {
+	panic("Not implemented")
+}

graphdb/conn_linux.go

@@ -0,0 +1,23 @@
+package graphdb
+
+import (
+	_ "code.google.com/p/gosqlite/sqlite3" // registers sqlite
+	"database/sql"
+	"os"
+)
+
+func NewSqliteConn(root string) (*Database, error) {
+	initDatabase := false
+	if _, err := os.Stat(root); err != nil {
+		if os.IsNotExist(err) {
+			initDatabase = true
+		} else {
+			return nil, err
+		}
+	}
+	conn, err := sql.Open("sqlite3", root)
+	if err != nil {
+		return nil, err
+	}
+	return NewDatabase(conn, initDatabase)
+}

graphdb/graphdb.go

@@ -0,0 +1,473 @@
+package graphdb
+
+import (
+	"database/sql"
+	"fmt"
+	"path"
+	"sync"
+)
+
+const (
+	createEntityTable = `
+    CREATE TABLE IF NOT EXISTS entity (
+        id text NOT NULL PRIMARY KEY
+    );`
+
+	createEdgeTable = `
+    CREATE TABLE IF NOT EXISTS edge (
+        "entity_id" text NOT NULL,
+        "parent_id" text NULL,
+        "name" text NOT NULL,
+        CONSTRAINT "parent_fk" FOREIGN KEY ("parent_id") REFERENCES "entity" ("id"),
+        CONSTRAINT "entity_fk" FOREIGN KEY ("entity_id") REFERENCES "entity" ("id")
+        );
+    `
+
+	createEdgeIndices = `
+    CREATE UNIQUE INDEX IF NOT EXISTS "name_parent_ix" ON "edge" (parent_id, name);
+    `
+)
+
+// Entity with a unique id
+type Entity struct {
+	id string
+}
+
+// An Edge connects two entities together
+type Edge struct {
+	EntityID string
+	Name     string
+	ParentID string
+}
+
+type Entities map[string]*Entity
+type Edges []*Edge
+
+type WalkFunc func(fullPath string, entity *Entity) error
+
+// Graph database for storing entities and their relationships
+type Database struct {
+	conn *sql.DB
+	mux  sync.RWMutex
+}
+
+// Create a new graph database initialized with a root entity
+func NewDatabase(conn *sql.DB, init bool) (*Database, error) {
+	if conn == nil {
+		return nil, fmt.Errorf("Database connection cannot be nil")
+	}
+	db := &Database{conn: conn}
+
+	if init {
+		if _, err := conn.Exec(createEntityTable); err != nil {
+			return nil, err
+		}
+		if _, err := conn.Exec(createEdgeTable); err != nil {
+			return nil, err
+		}
+		if _, err := conn.Exec(createEdgeIndices); err != nil {
+			return nil, err
+		}
+
+		rollback := func() {
+			conn.Exec("ROLLBACK")
+		}
+
+		// Create root entities
+		if _, err := conn.Exec("BEGIN"); err != nil {
+			return nil, err
+		}
+		if _, err := conn.Exec("INSERT INTO entity (id) VALUES (?);", "0"); err != nil {
+			rollback()
+			return nil, err
+		}
+
+		if _, err := conn.Exec("INSERT INTO edge (entity_id, name) VALUES(?,?);", "0", "/"); err != nil {
+			rollback()
+			return nil, err
+		}
+
+		if _, err := conn.Exec("COMMIT"); err != nil {
+			return nil, err
+		}
+	}
+	return db, nil
+}
+
+// Close the underlying connection to the database
+func (db *Database) Close() error {
+	return db.conn.Close()
+}
+
+// Set the entity id for a given path
+func (db *Database) Set(fullPath, id string) (*Entity, error) {
+	db.mux.Lock()
+	defer db.mux.Unlock()
+
+	rollback := func() {
+		db.conn.Exec("ROLLBACK")
+	}
+	if _, err := db.conn.Exec("BEGIN EXCLUSIVE"); err != nil {
+		return nil, err
+	}
+	var entityId string
+	if err := db.conn.QueryRow("SELECT id FROM entity WHERE id = ?;", id).Scan(&entityId); err != nil {
+		if err == sql.ErrNoRows {
+			if _, err := db.conn.Exec("INSERT INTO entity (id) VALUES(?);", id); err != nil {
+				rollback()
+				return nil, err
+			}
+		} else {
+			rollback()
+			return nil, err
+		}
+	}
+	e := &Entity{id}
+
+	parentPath, name := splitPath(fullPath)
+	if err := db.setEdge(parentPath, name, e); err != nil {
+		rollback()
+		return nil, err
+	}
+
+	if _, err := db.conn.Exec("COMMIT"); err != nil {
+		return nil, err
+	}
+	return e, nil
+}
+
+// Return true if a name already exists in the database
+func (db *Database) Exists(name string) bool {
+	db.mux.RLock()
+	defer db.mux.RUnlock()
+
+	e, err := db.get(name)
+	if err != nil {
+		return false
+	}
+	return e != nil
+}
+
+func (db *Database) setEdge(parentPath, name string, e *Entity) error {
+	parent, err := db.get(parentPath)
+	if err != nil {
+		return err
+	}
+	if parent.id == e.id {
+		return fmt.Errorf("Cannot set self as child")
+	}
+
+	if _, err := db.conn.Exec("INSERT INTO edge (parent_id, name, entity_id) VALUES (?,?,?);", parent.id, name, e.id); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Return the root "/" entity for the database
+func (db *Database) RootEntity() *Entity {
+	return &Entity{
+		id: "0",
+	}
+}
+
+// Return the entity for a given path
+func (db *Database) Get(name string) *Entity {
+	db.mux.RLock()
+	defer db.mux.RUnlock()
+
+	e, err := db.get(name)
+	if err != nil {
+		return nil
+	}
+	return e
+}
+
+func (db *Database) get(name string) (*Entity, error) {
+	e := db.RootEntity()
+	// We always know the root name so return it if
+	// it is requested
+	if name == "/" {
+		return e, nil
+	}
+
+	parts := split(name)
+	for i := 1; i < len(parts); i++ {
+		p := parts[i]
+		if p == "" {
+			continue
+		}
+
+		next := db.child(e, p)
+		if next == nil {
+			return nil, fmt.Errorf("Cannot find child for %s", name)
+		}
+		e = next
+	}
+	return e, nil
+
+}
+
+// List all entities by from the name
+// The key will be the full path of the entity
+func (db *Database) List(name string, depth int) Entities {
+	db.mux.RLock()
+	defer db.mux.RUnlock()
+
+	out := Entities{}
+	e, err := db.get(name)
+	if err != nil {
+		return out
+	}
+
+	children, err := db.children(e, name, depth, nil)
+	if err != nil {
+		return out
+	}
+
+	for _, c := range children {
+		out[c.FullPath] = c.Entity
+	}
+	return out
+}
+
+// Walk through the child graph of an entity, calling walkFunc for each child entity.
+// It is safe for walkFunc to call graph functions.
+func (db *Database) Walk(name string, walkFunc WalkFunc, depth int) error {
+	children, err := db.Children(name, depth)
+	if err != nil {
+		return err
+	}
+
+	// Note: the database lock must not be held while calling walkFunc
+	for _, c := range children {
+		if err := walkFunc(c.FullPath, c.Entity); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Return the children of the specified entity
+func (db *Database) Children(name string, depth int) ([]WalkMeta, error) {
+	db.mux.RLock()
+	defer db.mux.RUnlock()
+
+	e, err := db.get(name)
+	if err != nil {
+		return nil, err
+	}
+
+	return db.children(e, name, depth, nil)
+}
+
+// Return the refrence count for a specified id
+func (db *Database) Refs(id string) int {
+	db.mux.RLock()
+	defer db.mux.RUnlock()
+
+	var count int
+	if err := db.conn.QueryRow("SELECT COUNT(*) FROM edge WHERE entity_id = ?;", id).Scan(&count); err != nil {
+		return 0
+	}
+	return count
+}
+
+// Return all the id's path references
+func (db *Database) RefPaths(id string) Edges {
+	db.mux.RLock()
+	defer db.mux.RUnlock()
+
+	refs := Edges{}
+
+	rows, err := db.conn.Query("SELECT name, parent_id FROM edge WHERE entity_id = ?;", id)
+	if err != nil {
+		return refs
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var name string
+		var parentId string
+		if err := rows.Scan(&name, &parentId); err != nil {
+			return refs
+		}
+		refs = append(refs, &Edge{
+			EntityID: id,
+			Name:     name,
+			ParentID: parentId,
+		})
+	}
+	return refs
+}
+
+// Delete the reference to an entity at a given path
+func (db *Database) Delete(name string) error {
+	db.mux.Lock()
+	defer db.mux.Unlock()
+
+	if name == "/" {
+		return fmt.Errorf("Cannot delete root entity")
+	}
+
+	parentPath, n := splitPath(name)
+	parent, err := db.get(parentPath)
+	if err != nil {
+		return err
+	}
+
+	if _, err := db.conn.Exec("DELETE FROM edge WHERE parent_id = ? AND name = ?;", parent.id, n); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Remove the entity with the specified id
+// Walk the graph to make sure all references to the entity
+// are removed and return the number of references removed
+func (db *Database) Purge(id string) (int, error) {
+	db.mux.Lock()
+	defer db.mux.Unlock()
+
+	rollback := func() {
+		db.conn.Exec("ROLLBACK")
+	}
+
+	if _, err := db.conn.Exec("BEGIN"); err != nil {
+		return -1, err
+	}
+
+	// Delete all edges
+	rows, err := db.conn.Exec("DELETE FROM edge WHERE entity_id = ?;", id)
+	if err != nil {
+		rollback()
+		return -1, err
+	}
+
+	changes, err := rows.RowsAffected()
+	if err != nil {
+		return -1, err
+	}
+
+	// Delete entity
+	if _, err := db.conn.Exec("DELETE FROM entity where id = ?;", id); err != nil {
+		rollback()
+		return -1, err
+	}
+
+	if _, err := db.conn.Exec("COMMIT"); err != nil {
+		return -1, err
+	}
+	return int(changes), nil
+}
+
+// Rename an edge for a given path
+func (db *Database) Rename(currentName, newName string) error {
+	db.mux.Lock()
+	defer db.mux.Unlock()
+
+	parentPath, name := splitPath(currentName)
+	newParentPath, newEdgeName := splitPath(newName)
+
+	if parentPath != newParentPath {
+		return fmt.Errorf("Cannot rename when root paths do not match %s != %s", parentPath, newParentPath)
+	}
+
+	parent, err := db.get(parentPath)
+	if err != nil {
+		return err
+	}
+
+	rows, err := db.conn.Exec("UPDATE edge SET name = ? WHERE parent_id = ? AND name = ?;", newEdgeName, parent.id, name)
+	if err != nil {
+		return err
+	}
+	i, err := rows.RowsAffected()
+	if err != nil {
+		return err
+	}
+	if i == 0 {
+		return fmt.Errorf("Cannot locate edge for %s %s", parent.id, name)
+	}
+	return nil
+}
+
+type WalkMeta struct {
+	Parent   *Entity
+	Entity   *Entity
+	FullPath string
+	Edge     *Edge
+}
+
+func (db *Database) children(e *Entity, name string, depth int, entities []WalkMeta) ([]WalkMeta, error) {
+	if e == nil {
+		return entities, nil
+	}
+
+	rows, err := db.conn.Query("SELECT entity_id, name FROM edge where parent_id = ?;", e.id)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var entityId, entityName string
+		if err := rows.Scan(&entityId, &entityName); err != nil {
+			return nil, err
+		}
+		child := &Entity{entityId}
+		edge := &Edge{
+			ParentID: e.id,
+			Name:     entityName,
+			EntityID: child.id,
+		}
+
+		meta := WalkMeta{
+			Parent:   e,
+			Entity:   child,
+			FullPath: path.Join(name, edge.Name),
+			Edge:     edge,
+		}
+
+		entities = append(entities, meta)
+
+		if depth != 0 {
+			nDepth := depth
+			if depth != -1 {
+				nDepth -= 1
+			}
+			entities, err = db.children(child, meta.FullPath, nDepth, entities)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return entities, nil
+}
+
+// Return the entity based on the parent path and name
+func (db *Database) child(parent *Entity, name string) *Entity {
+	var id string
+	if err := db.conn.QueryRow("SELECT entity_id FROM edge WHERE parent_id = ? AND name = ?;", parent.id, name).Scan(&id); err != nil {
+		return nil
+	}
+	return &Entity{id}
+}
+
+// Return the id used to reference this entity
+func (e *Entity) ID() string {
+	return e.id
+}
+
+// Return the paths sorted by depth
+func (e Entities) Paths() []string {
+	out := make([]string, len(e))
+	var i int
+	for k := range e {
+		out[i] = k
+		i++
+	}
+	sortByDepth(out)
+
+	return out
+}

graphdb/graphdb_test.go

@@ -0,0 +1,540 @@
+package graphdb
+
+import (
+	_ "code.google.com/p/gosqlite/sqlite3"
+	"database/sql"
+	"fmt"
+	"os"
+	"path"
+	"strconv"
+	"testing"
+)
+
+func newTestDb(t *testing.T) (*Database, string) {
+	p := path.Join(os.TempDir(), "sqlite.db")
+	conn, err := sql.Open("sqlite3", p)
+	db, err := NewDatabase(conn, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return db, p
+}
+
+func destroyTestDb(dbPath string) {
+	os.Remove(dbPath)
+}
+
+func TestNewDatabase(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	if db == nil {
+		t.Fatal("Database should not be nil")
+	}
+	db.Close()
+	defer destroyTestDb(dbpath)
+}
+
+func TestCreateRootEnity(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+	root := db.RootEntity()
+	if root == nil {
+		t.Fatal("Root entity should not be nil")
+	}
+}
+
+func TestGetRootEntity(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	e := db.Get("/")
+	if e == nil {
+		t.Fatal("Entity should not be nil")
+	}
+	if e.ID() != "0" {
+		t.Fatalf("Enity id should be 0, got %s", e.ID())
+	}
+}
+
+func TestSetEntityWithDifferentName(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/test", "1")
+	if _, err := db.Set("/other", "1"); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestSetDuplicateEntity(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	if _, err := db.Set("/foo", "42"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/foo", "43"); err == nil {
+		t.Fatalf("Creating an entry with a duplciate path did not cause an error")
+	}
+}
+
+func TestCreateChild(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	child, err := db.Set("/db", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if child == nil {
+		t.Fatal("Child should not be nil")
+	}
+	if child.ID() != "1" {
+		t.Fail()
+	}
+}
+
+func TestListAllRootChildren(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	for i := 1; i < 6; i++ {
+		a := strconv.Itoa(i)
+		if _, err := db.Set("/"+a, a); err != nil {
+			t.Fatal(err)
+		}
+	}
+	entries := db.List("/", -1)
+	if len(entries) != 5 {
+		t.Fatalf("Expect 5 entries for / got %d", len(entries))
+	}
+}
+
+func TestListAllSubChildren(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	_, err := db.Set("/webapp", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child2, err := db.Set("/db", "2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child4, err := db.Set("/logs", "4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/db/logs", child4.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child3, err := db.Set("/sentry", "3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/sentry", child3.ID()); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/db", child2.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	entries := db.List("/webapp", 1)
+	if len(entries) != 3 {
+		t.Fatalf("Expect 3 entries for / got %d", len(entries))
+	}
+
+	entries = db.List("/webapp", 0)
+	if len(entries) != 2 {
+		t.Fatalf("Expect 2 entries for / got %d", len(entries))
+	}
+}
+
+func TestAddSelfAsChild(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	child, err := db.Set("/test", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/test/other", child.ID()); err == nil {
+		t.Fatal("Error should not be nil")
+	}
+}
+
+func TestAddChildToNonExistantRoot(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	if _, err := db.Set("/myapp", "1"); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := db.Set("/myapp/proxy/db", "2"); err == nil {
+		t.Fatal("Error should not be nil")
+	}
+}
+
+func TestWalkAll(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+	_, err := db.Set("/webapp", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child2, err := db.Set("/db", "2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child4, err := db.Set("/db/logs", "4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/logs", child4.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child3, err := db.Set("/sentry", "3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/sentry", child3.ID()); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/db", child2.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child5, err := db.Set("/gograph", "5")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/same-ref-diff-name", child5.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := db.Walk("/", func(p string, e *Entity) error {
+		t.Logf("Path: %s Entity: %s", p, e.ID())
+		return nil
+	}, -1); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGetEntityByPath(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+	_, err := db.Set("/webapp", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child2, err := db.Set("/db", "2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child4, err := db.Set("/logs", "4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/db/logs", child4.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child3, err := db.Set("/sentry", "3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/sentry", child3.ID()); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/db", child2.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child5, err := db.Set("/gograph", "5")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/same-ref-diff-name", child5.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	entity := db.Get("/webapp/db/logs")
+	if entity == nil {
+		t.Fatal("Entity should not be nil")
+	}
+	if entity.ID() != "4" {
+		t.Fatalf("Expected to get entity with id 4, got %s", entity.ID())
+	}
+}
+
+func TestEnitiesPaths(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+	_, err := db.Set("/webapp", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child2, err := db.Set("/db", "2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child4, err := db.Set("/logs", "4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/db/logs", child4.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child3, err := db.Set("/sentry", "3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/sentry", child3.ID()); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/db", child2.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child5, err := db.Set("/gograph", "5")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/same-ref-diff-name", child5.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	out := db.List("/", -1)
+	for _, p := range out.Paths() {
+		t.Log(p)
+	}
+}
+
+func TestDeleteRootEntity(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	if err := db.Delete("/"); err == nil {
+		t.Fatal("Error should not be nil")
+	}
+}
+
+func TestDeleteEntity(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+	_, err := db.Set("/webapp", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child2, err := db.Set("/db", "2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	child4, err := db.Set("/logs", "4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/db/logs", child4.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child3, err := db.Set("/sentry", "3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/sentry", child3.ID()); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/db", child2.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	child5, err := db.Set("/gograph", "5")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := db.Set("/webapp/same-ref-diff-name", child5.ID()); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := db.Delete("/webapp/sentry"); err != nil {
+		t.Fatal(err)
+	}
+	entity := db.Get("/webapp/sentry")
+	if entity != nil {
+		t.Fatal("Entity /webapp/sentry should be nil")
+	}
+}
+
+func TestCountRefs(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/webapp", "1")
+
+	if db.Refs("1") != 1 {
+		t.Fatal("Expect reference count to be 1")
+	}
+
+	db.Set("/db", "2")
+	db.Set("/webapp/db", "2")
+	if db.Refs("2") != 2 {
+		t.Fatal("Expect reference count to be 2")
+	}
+}
+
+func TestPurgeId(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/webapp", "1")
+
+	if db.Refs("1") != 1 {
+		t.Fatal("Expect reference count to be 1")
+	}
+
+	db.Set("/db", "2")
+	db.Set("/webapp/db", "2")
+
+	count, err := db.Purge("2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if count != 2 {
+		t.Fatal("Expected 2 references to be removed")
+	}
+}
+
+func TestRename(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/webapp", "1")
+
+	if db.Refs("1") != 1 {
+		t.Fatal("Expect reference count to be 1")
+	}
+
+	db.Set("/db", "2")
+	db.Set("/webapp/db", "2")
+
+	if db.Get("/webapp/db") == nil {
+		t.Fatal("Cannot find entity at path /webapp/db")
+	}
+
+	if err := db.Rename("/webapp/db", "/webapp/newdb"); err != nil {
+		t.Fatal(err)
+	}
+	if db.Get("/webapp/db") != nil {
+		t.Fatal("Entity should not exist at /webapp/db")
+	}
+	if db.Get("/webapp/newdb") == nil {
+		t.Fatal("Cannot find entity at path /webapp/newdb")
+	}
+
+}
+
+func TestCreateMultipleNames(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/db", "1")
+	if _, err := db.Set("/myapp", "1"); err != nil {
+		t.Fatal(err)
+	}
+
+	db.Walk("/", func(p string, e *Entity) error {
+		t.Logf("%s\n", p)
+		return nil
+	}, -1)
+}
+
+func TestRefPaths(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/webapp", "1")
+
+	db.Set("/db", "2")
+	db.Set("/webapp/db", "2")
+
+	refs := db.RefPaths("2")
+	if len(refs) != 2 {
+		t.Fatalf("Expected reference count to be 2, got %d", len(refs))
+	}
+}
+
+func TestExistsTrue(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/testing", "1")
+
+	if !db.Exists("/testing") {
+		t.Fatalf("/tesing should exist")
+	}
+}
+
+func TestExistsFalse(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/toerhe", "1")
+
+	if db.Exists("/testing") {
+		t.Fatalf("/tesing should not exist")
+	}
+
+}
+
+func TestGetNameWithTrailingSlash(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/todo", "1")
+
+	e := db.Get("/todo/")
+	if e == nil {
+		t.Fatalf("Entity should not be nil")
+	}
+}
+
+func TestConcurrentWrites(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	errs := make(chan error, 2)
+
+	save := func(name string, id string) {
+		if _, err := db.Set(fmt.Sprintf("/%s", name), id); err != nil {
+			errs <- err
+		}
+		errs <- nil
+	}
+	purge := func(id string) {
+		if _, err := db.Purge(id); err != nil {
+			errs <- err
+		}
+		errs <- nil
+	}
+
+	save("/1", "1")
+
+	go purge("1")
+	go save("/2", "2")
+
+	any := false
+	for i := 0; i < 2; i++ {
+		if err := <-errs; err != nil {
+			any = true
+			t.Log(err)
+		}
+	}
+	if any {
+		t.Fatal()
+	}
+}

graphdb/sort.go

@@ -0,0 +1,27 @@
+package graphdb
+
+import "sort"
+
+type pathSorter struct {
+	paths []string
+	by    func(i, j string) bool
+}
+
+func sortByDepth(paths []string) {
+	s := &pathSorter{paths, func(i, j string) bool {
+		return PathDepth(i) > PathDepth(j)
+	}}
+	sort.Sort(s)
+}
+
+func (s *pathSorter) Len() int {
+	return len(s.paths)
+}
+
+func (s *pathSorter) Swap(i, j int) {
+	s.paths[i], s.paths[j] = s.paths[j], s.paths[i]
+}
+
+func (s *pathSorter) Less(i, j int) bool {
+	return s.by(s.paths[i], s.paths[j])
+}

graphdb/sort_test.go

@@ -0,0 +1,29 @@
+package graphdb
+
+import (
+	"testing"
+)
+
+func TestSort(t *testing.T) {
+	paths := []string{
+		"/",
+		"/myreallylongname",
+		"/app/db",
+	}
+
+	sortByDepth(paths)
+
+	if len(paths) != 3 {
+		t.Fatalf("Expected 3 parts got %d", len(paths))
+	}
+
+	if paths[0] != "/app/db" {
+		t.Fatalf("Expected /app/db got %s", paths[0])
+	}
+	if paths[1] != "/myreallylongname" {
+		t.Fatalf("Expected /myreallylongname got %s", paths[1])
+	}
+	if paths[2] != "/" {
+		t.Fatalf("Expected / got %s", paths[2])
+	}
+}

graphdb/utils.go

@@ -0,0 +1,32 @@
+package graphdb
+
+import (
+	"path"
+	"strings"
+)
+
+// Split p on /
+func split(p string) []string {
+	return strings.Split(p, "/")
+}
+
+// Returns the depth or number of / in a given path
+func PathDepth(p string) int {
+	parts := split(p)
+	if len(parts) == 2 && parts[1] == "" {
+		return 1
+	}
+	return len(parts)
+}
+
+func splitPath(p string) (parent, name string) {
+	if p[0] != '/' {
+		p = "/" + p
+	}
+	parent, name = path.Split(p)
+	l := len(parent)
+	if parent[l-1] == '/' {
+		parent = parent[:l-1]
+	}
+	return
+}