support nested transactions

lib/Connection.php

@@ -77,6 +77,12 @@ abstract class Connection
 	 */
 	static $DEFAULT_PORT = 0;
 
+    /**
+     * Number of nested transactions
+     * @var int
+     */
+    static protected $transaction_counter = 0;
+
 	/**
 	 * Retrieve a database connection.
 	 *
@@ -376,15 +382,26 @@ public function tables()
 	 */
 	public function transaction()
 	{
-		if (!$this->connection->beginTransaction())
-			throw new DatabaseException($this);
+        // Transaction started already
+        if (static::$transaction_counter++) {
+            $this->connection->exec('SAVEPOINT trans'.static::$transaction_counter);
+            return;
+        }
+
+        if (!$this->connection->beginTransaction())
+           throw new DatabaseException($this);
 	}
 
 	/**
 	 * Commits the current transaction.
 	 */
 	public function commit()
 	{
+        // Nested transaction simply decrease number
+        if (--static::$transaction_counter) {
+            return;
+        }
+
 		if (!$this->connection->commit())
 			throw new DatabaseException($this);
 	}
@@ -394,6 +411,11 @@ public function commit()
 	 */
 	public function rollback()
 	{
+        if (--static::$transaction_counter) {
+            $this->connection->exec('ROLLBACK TO trans'.(static::$transaction_counter + 1));
+            return true;
+        }
+
 		if (!$this->connection->rollback())
 			throw new DatabaseException($this);
 	}

test/helpers/AdapterTest.php

@@ -407,5 +407,34 @@ public function test_date_to_string()
 		$datetime = '2009-01-01';
 		$this->assert_equals($datetime,$this->conn->date_to_string(date_create($datetime)));
 	}
+
+
+    public function test_transaction_nested_commit()
+    {
+        $original = $this->conn->query_and_fetch_one("select count(*) from authors");
+
+        $this->conn->transaction();
+        $this->conn->query("insert into authors(author_id,name) values(9998,'blahhhhhhhh')");
+        // Nested
+        $this->conn->transaction();
+        $this->conn->query("insert into authors(author_id,name) values(9999,'blahhhhhhhh')");
+        $this->conn->commit();
+
+        // Another nested
+        try {
+            $this->conn->transaction();
+            $this->conn->query("insert into authors(author_id,name) values(9999,'blahhhhhhhh')"); // fails
+            $this->conn->commit();
+        }
+        catch (Exception $e)
+        {
+            $this->conn->rollback();
+        }
+
+        // Commit primary transaction
+        $this->conn->commit();
+
+        $this->assert_equals($original+2, $this->conn->query_and_fetch_one("select count(*) from authors"));
+    }
 }
 ?>