From 14803cda500f7daea345cccc5c72399f2ab6f1f2 Mon Sep 17 00:00:00 2001
From: unclejack <unclejacksons@gmail.com>
Date: Fri, 19 Dec 2014 13:57:21 +0200
Subject: [PATCH] pkg/graphdb: use transactions for transactions

Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com>
---
 graphdb/graphdb.go | 88 +++++++++++++++++++++-------------------------
 1 file changed, 41 insertions(+), 47 deletions(-)

diff --git a/graphdb/graphdb.go b/graphdb/graphdb.go
index 6234203..c6f13ed 100644
--- a/graphdb/graphdb.go
+++ b/graphdb/graphdb.go
@@ -79,46 +79,43 @@ func NewDatabase(conn *sql.DB) (*Database, error) {
 	}
 	db := &Database{conn: conn}
 
-	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 {
+	tx, err := conn.Begin()
+	if err != nil {
 		return nil, err
 	}
 
-	if _, err := conn.Exec("DELETE FROM entity where id = ?", "0"); err != nil {
-		rollback()
+	if _, err := tx.Exec(createEntityTable); err != nil {
+		return nil, err
+	}
+	if _, err := tx.Exec(createEdgeTable); err != nil {
+		return nil, err
+	}
+	if _, err := tx.Exec(createEdgeIndices); err != nil {
 		return nil, err
 	}
 
-	if _, err := conn.Exec("INSERT INTO entity (id) VALUES (?);", "0"); err != nil {
-		rollback()
+	if _, err := tx.Exec("DELETE FROM entity where id = ?", "0"); err != nil {
+		tx.Rollback()
 		return nil, err
 	}
 
-	if _, err := conn.Exec("DELETE FROM edge where entity_id=? and name=?", "0", "/"); err != nil {
-		rollback()
+	if _, err := tx.Exec("INSERT INTO entity (id) VALUES (?);", "0"); err != nil {
+		tx.Rollback()
 		return nil, err
 	}
 
-	if _, err := conn.Exec("INSERT INTO edge (entity_id, name) VALUES(?,?);", "0", "/"); err != nil {
-		rollback()
+	if _, err := tx.Exec("DELETE FROM edge where entity_id=? and name=?", "0", "/"); err != nil {
+		tx.Rollback()
 		return nil, err
 	}
 
-	if _, err := conn.Exec("COMMIT"); err != nil {
+	if _, err := tx.Exec("INSERT INTO edge (entity_id, name) VALUES(?,?);", "0", "/"); err != nil {
+		tx.Rollback()
+		return nil, err
+	}
+
+	if err := tx.Commit(); err != nil {
 		return nil, err
 	}
 
@@ -135,33 +132,32 @@ 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 {
+	tx, err := db.conn.Begin()
+	if 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 := tx.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()
+			if _, err := tx.Exec("INSERT INTO entity (id) VALUES(?);", id); err != nil {
+				tx.Rollback()
 				return nil, err
 			}
 		} else {
-			rollback()
+			tx.Rollback()
 			return nil, err
 		}
 	}
 	e := &Entity{id}
 
 	parentPath, name := splitPath(fullPath)
-	if err := db.setEdge(parentPath, name, e); err != nil {
-		rollback()
+	if err := db.setEdge(parentPath, name, e, tx); err != nil {
+		tx.Rollback()
 		return nil, err
 	}
 
-	if _, err := db.conn.Exec("COMMIT"); err != nil {
+	if err := tx.Commit(); err != nil {
 		return nil, err
 	}
 	return e, nil
@@ -179,7 +175,7 @@ func (db *Database) Exists(name string) bool {
 	return e != nil
 }
 
-func (db *Database) setEdge(parentPath, name string, e *Entity) error {
+func (db *Database) setEdge(parentPath, name string, e *Entity, tx *sql.Tx) error {
 	parent, err := db.get(parentPath)
 	if err != nil {
 		return err
@@ -188,7 +184,7 @@ func (db *Database) setEdge(parentPath, name string, e *Entity) error {
 		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 {
+	if _, err := tx.Exec("INSERT INTO edge (parent_id, name, entity_id) VALUES (?,?,?);", parent.id, name, e.id); err != nil {
 		return err
 	}
 	return nil
@@ -371,18 +367,15 @@ 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 {
+	tx, err := db.conn.Begin()
+	if err != nil {
 		return -1, err
 	}
 
 	// Delete all edges
-	rows, err := db.conn.Exec("DELETE FROM edge WHERE entity_id = ?;", id)
+	rows, err := tx.Exec("DELETE FROM edge WHERE entity_id = ?;", id)
 	if err != nil {
-		rollback()
+		tx.Rollback()
 		return -1, err
 	}
 
@@ -392,14 +385,15 @@ func (db *Database) Purge(id string) (int, error) {
 	}
 
 	// Delete entity
-	if _, err := db.conn.Exec("DELETE FROM entity where id = ?;", id); err != nil {
-		rollback()
+	if _, err := tx.Exec("DELETE FROM entity where id = ?;", id); err != nil {
+		tx.Rollback()
 		return -1, err
 	}
 
-	if _, err := db.conn.Exec("COMMIT"); err != nil {
+	if err := tx.Commit(); err != nil {
 		return -1, err
 	}
+
 	return int(changes), nil
 }