Fix #4171 and a number of other transaction bugs

15 files changed, 170 insertions, 356 deletions

diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index cc94edc16..0ea679432 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -668,7 +668,13 @@ abstract class CI_DB_driver {
 				{
 					do
 					{
+						$trans_depth = $this->_trans_depth;
 						$this->trans_complete();
+						if ($trans_depth === $this->_trans_depth)
+						{
+							log_message('error', 'Database: Failure during an automated transaction commit/rollback!');
+							break;
+						}
 					}
 					while ($this->_trans_depth !== 0);
 				}
@@ -813,24 +819,16 @@ abstract class CI_DB_driver {
 	 * Start Transaction
 	 *
 	 * @param	bool	$test_mode = FALSE
-	 * @return	void
+	 * @return	bool
 	 */
 	public function trans_start($test_mode = FALSE)
 	{
 		if ( ! $this->trans_enabled)
 		{
-			return;
-		}
-
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ($this->_trans_depth > 0)
-		{
-			$this->_trans_depth += 1;
-			return;
+			return FALSE;
 		}
 
-		$this->trans_begin($test_mode);
-		$this->_trans_depth += 1;
+		return $this->trans_begin($test_mode);
 	}
 
 	// --------------------------------------------------------------------
@@ -847,17 +845,6 @@ abstract class CI_DB_driver {
 			return FALSE;
 		}
 
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ($this->_trans_depth > 1)
-		{
-			$this->_trans_depth -= 1;
-			return TRUE;
-		}
-		else
-		{
-			$this->_trans_depth = 0;
-		}
-
 		// The query() function will set this flag to FALSE in the event that a query failed
 		if ($this->_trans_status === FALSE OR $this->_trans_failure === TRUE)
 		{
@@ -875,8 +862,7 @@ abstract class CI_DB_driver {
 			return FALSE;
 		}
 
-		$this->trans_commit();
-		return TRUE;
+		return $this->trans_commit();
 	}
 
 	// --------------------------------------------------------------------
@@ -894,6 +880,87 @@ abstract class CI_DB_driver {
 	// --------------------------------------------------------------------
 
 	/**
+	 * Begin Transaction
+	 *
+	 * @param	bool	$test_mode
+	 * @return	bool
+	 */
+	public function trans_begin($test_mode = FALSE)
+	{
+		if ( ! $this->trans_enabled)
+		{
+			return FALSE;
+		}
+		// When transactions are nested we only begin/commit/rollback the outermost ones
+		elseif ($this->_trans_depth > 0)
+		{
+			$this->_trans_depth++;
+			return TRUE;
+		}
+
+		// Reset the transaction failure flag.
+		// If the $test_mode flag is set to TRUE transactions will be rolled back
+		// even if the queries produce a successful result.
+		$this->_trans_failure = ($test_mode === TRUE);
+
+		if ($this->_trans_begin())
+		{
+			$this->_trans_depth++;
+			return TRUE;
+		}
+
+		return FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Commit Transaction
+	 *
+	 * @return	bool
+	 */
+	public function trans_commit()
+	{
+		if ( ! $this->trans_enabled OR $this->_trans_depth === 0)
+		{
+			return FALSE;
+		}
+		// When transactions are nested we only begin/commit/rollback the outermost ones
+		elseif ($this->_trans_depth > 1 OR $this->_trans_commit())
+		{
+			$this->_trans_depth--;
+			return TRUE;
+		}
+
+		return FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Rollback Transaction
+	 *
+	 * @return	bool
+	 */
+	public function trans_rollback()
+	{
+		if ( ! $this->trans_enabled OR $this->_trans_depth === 0)
+		{
+			return FALSE;
+		}
+		// When transactions are nested we only begin/commit/rollback the outermost ones
+		elseif ($this->_trans_depth > 1 OR $this->_trans_rollback())
+		{
+			$this->_trans_depth--;
+			return TRUE;
+		}
+
+		return FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Compile Bindings
 	 *
 	 * @param	string	the sql statement
diff --git a/system/database/drivers/cubrid/cubrid_driver.php b/system/database/drivers/cubrid/cubrid_driver.php
index f80b4db54..65f4adb3f 100644
--- a/system/database/drivers/cubrid/cubrid_driver.php
+++ b/system/database/drivers/cubrid/cubrid_driver.php
@@ -187,25 +187,17 @@ class CI_DB_cubrid_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if (($autocommit = cubrid_get_autocommit($this->conn_id)) === NULL)
 		{
-			return TRUE;
+			return FALSE;
 		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
-		if (cubrid_get_autocommit($this->conn_id))
+		elseif ($autocommit === TRUE)
 		{
-			cubrid_set_autocommit($this->conn_id, CUBRID_AUTOCOMMIT_FALSE);
+			return cubrid_set_autocommit($this->conn_id, CUBRID_AUTOCOMMIT_FALSE);
 		}
 
 		return TRUE;
@@ -218,19 +210,16 @@ class CI_DB_cubrid_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if ( ! cubrid_commit($this->conn_id))
 		{
-			return TRUE;
+			return FALSE;
 		}
 
-		cubrid_commit($this->conn_id);
-
 		if ($this->auto_commit && ! cubrid_get_autocommit($this->conn_id))
 		{
-			cubrid_set_autocommit($this->conn_id, CUBRID_AUTOCOMMIT_TRUE);
+			return cubrid_set_autocommit($this->conn_id, CUBRID_AUTOCOMMIT_TRUE);
 		}
 
 		return TRUE;
@@ -243,16 +232,13 @@ class CI_DB_cubrid_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if ( ! cubrid_rollback($this->conn_id))
 		{
-			return TRUE;
+			return FALSE;
 		}
 
-		cubrid_rollback($this->conn_id);
-
 		if ($this->auto_commit && ! cubrid_get_autocommit($this->conn_id))
 		{
 			cubrid_set_autocommit($this->conn_id, CUBRID_AUTOCOMMIT_TRUE);
diff --git a/system/database/drivers/ibase/ibase_driver.php b/system/database/drivers/ibase/ibase_driver.php
index 529c320cd..82550d51b 100644
--- a/system/database/drivers/ibase/ibase_driver.php
+++ b/system/database/drivers/ibase/ibase_driver.php
@@ -134,24 +134,16 @@ class CI_DB_ibase_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if (($trans_handle = ibase_trans($this->conn_id)) === FALSE)
 		{
-			return TRUE;
+			return FALSE;
 		}
 
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
-		$this->_ibase_trans = ibase_trans($this->conn_id);
-
+		$this->_ibase_trans = $trans_handle;
 		return TRUE;
 	}
 
@@ -162,15 +154,15 @@ class CI_DB_ibase_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans->depth > 0)
+		if (ibase_commit($this->_ibase_trans))
 		{
+			$this->_ibase_trans = NULL;
 			return TRUE;
 		}
 
-		return ibase_commit($this->_ibase_trans);
+		return FALSE;
 	}
 
 	// --------------------------------------------------------------------
@@ -180,15 +172,15 @@ class CI_DB_ibase_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if (ibase_rollback($this->_ibase_trans))
 		{
+			$this->_ibase_trans = NULL;
 			return TRUE;
 		}
 
-		return ibase_rollback($this->_ibase_trans);
+		return FALSE;
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/mssql/mssql_driver.php b/system/database/drivers/mssql/mssql_driver.php
index 05e5418c3..883973ae1 100644
--- a/system/database/drivers/mssql/mssql_driver.php
+++ b/system/database/drivers/mssql/mssql_driver.php
@@ -182,22 +182,10 @@ class CI_DB_mssql_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		return $this->simple_query('BEGIN TRAN');
 	}
 
@@ -208,14 +196,8 @@ class CI_DB_mssql_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return $this->simple_query('COMMIT TRAN');
 	}
 
@@ -226,14 +208,8 @@ class CI_DB_mssql_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return $this->simple_query('ROLLBACK TRAN');
 	}
 
diff --git a/system/database/drivers/mysql/mysql_driver.php b/system/database/drivers/mysql/mysql_driver.php
index df0f24920..9c630d0d6 100644
--- a/system/database/drivers/mysql/mysql_driver.php
+++ b/system/database/drivers/mysql/mysql_driver.php
@@ -272,25 +272,12 @@ class CI_DB_mysql_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		$this->simple_query('SET AUTOCOMMIT=0');
-		$this->simple_query('START TRANSACTION'); // can also be BEGIN or BEGIN WORK
-		return TRUE;
+		return $this->simple_query('START TRANSACTION'); // can also be BEGIN or BEGIN WORK
 	}
 
 	// --------------------------------------------------------------------
@@ -300,17 +287,15 @@ class CI_DB_mysql_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if ($this->simple_query('COMMIT'))
 		{
+			$this->simple_query('SET AUTOCOMMIT=1');
 			return TRUE;
 		}
 
-		$this->simple_query('COMMIT');
-		$this->simple_query('SET AUTOCOMMIT=1');
-		return TRUE;
+		return FALSE;
 	}
 
 	// --------------------------------------------------------------------
@@ -320,17 +305,15 @@ class CI_DB_mysql_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if ($this->simple_query('ROLLBACK'))
 		{
+			$this->simple_query('SET AUTOCOMMIT=1');
 			return TRUE;
 		}
 
-		$this->simple_query('ROLLBACK');
-		$this->simple_query('SET AUTOCOMMIT=1');
-		return TRUE;
+		return FALSE;
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index dd3cc77c6..827470078 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -291,22 +291,10 @@ class CI_DB_mysqli_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		$this->conn_id->autocommit(FALSE);
 		return is_php('5.5')
 			? $this->conn_id->begin_transaction()
@@ -320,14 +308,8 @@ class CI_DB_mysqli_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		if ($this->conn_id->commit())
 		{
 			$this->conn_id->autocommit(TRUE);
@@ -344,14 +326,8 @@ class CI_DB_mysqli_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		if ($this->conn_id->rollback())
 		{
 			$this->conn_id->autocommit(TRUE);
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index f2e40da9b..916ddeb90 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -378,27 +378,10 @@ class CI_DB_oci8_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		if ( ! $this->trans_enabled)
-		{
-			return TRUE;
-		}
-
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ($this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		$this->commit_mode = is_php('5.3.2') ? OCI_NO_AUTO_COMMIT : OCI_DEFAULT;
 		return TRUE;
 	}
@@ -410,20 +393,10 @@ class CI_DB_oci8_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		if ( ! $this->trans_enabled)
-		{
-			return TRUE;
-		}
-
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ($this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		$this->commit_mode = OCI_COMMIT_ON_SUCCESS;
+
 		return oci_commit($this->conn_id);
 	}
 
@@ -434,14 +407,8 @@ class CI_DB_oci8_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		$this->commit_mode = OCI_COMMIT_ON_SUCCESS;
 		return oci_rollback($this->conn_id);
 	}
diff --git a/system/database/drivers/odbc/odbc_driver.php b/system/database/drivers/odbc/odbc_driver.php
index f5d77a147..409284b44 100644
--- a/system/database/drivers/odbc/odbc_driver.php
+++ b/system/database/drivers/odbc/odbc_driver.php
@@ -143,22 +143,10 @@ class CI_DB_odbc_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		return odbc_autocommit($this->conn_id, FALSE);
 	}
 
@@ -169,17 +157,15 @@ class CI_DB_odbc_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if (odbc_commit($this->conn_id))
 		{
+			odbc_autocommit($this->conn_id, TRUE);
 			return TRUE;
 		}
 
-		$ret = odbc_commit($this->conn_id);
-		odbc_autocommit($this->conn_id, TRUE);
-		return $ret;
+		return FALSE;
 	}
 
 	// --------------------------------------------------------------------
@@ -189,17 +175,15 @@ class CI_DB_odbc_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
+		if (odbc_rollback($this->conn_id))
 		{
+			odbc_autocommit($this->conn_id, TRUE);
 			return TRUE;
 		}
 
-		$ret = odbc_rollback($this->conn_id);
-		odbc_autocommit($this->conn_id, TRUE);
-		return $ret;
+		return FALSE;
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/pdo/pdo_driver.php b/system/database/drivers/pdo/pdo_driver.php
index cc77e9568..8c5a5e7e3 100644
--- a/system/database/drivers/pdo/pdo_driver.php
+++ b/system/database/drivers/pdo/pdo_driver.php
@@ -186,22 +186,10 @@ class CI_DB_pdo_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		return $this->conn_id->beginTransaction();
 	}
 
@@ -212,14 +200,8 @@ class CI_DB_pdo_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return $this->conn_id->commit();
 	}
 
@@ -230,14 +212,8 @@ class CI_DB_pdo_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return $this->conn_id->rollBack();
 	}
 
diff --git a/system/database/drivers/postgre/postgre_driver.php b/system/database/drivers/postgre/postgre_driver.php
index 7be07c3bf..b1df326f7 100644
--- a/system/database/drivers/postgre/postgre_driver.php
+++ b/system/database/drivers/postgre/postgre_driver.php
@@ -247,22 +247,10 @@ class CI_DB_postgre_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		return (bool) pg_query($this->conn_id, 'BEGIN');
 	}
 
@@ -273,14 +261,8 @@ class CI_DB_postgre_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return (bool) pg_query($this->conn_id, 'COMMIT');
 	}
 
@@ -291,14 +273,8 @@ class CI_DB_postgre_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return (bool) pg_query($this->conn_id, 'ROLLBACK');
 	}
 
diff --git a/system/database/drivers/sqlite/sqlite_driver.php b/system/database/drivers/sqlite/sqlite_driver.php
index 9d9caa0b4..e000a8e50 100644
--- a/system/database/drivers/sqlite/sqlite_driver.php
+++ b/system/database/drivers/sqlite/sqlite_driver.php
@@ -122,24 +122,11 @@ class CI_DB_sqlite_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
-		$this->simple_query('BEGIN TRANSACTION');
-		return TRUE;
+		return $this->simple_query('BEGIN TRANSACTION');
 	}
 
 	// --------------------------------------------------------------------
@@ -149,16 +136,9 @@ class CI_DB_sqlite_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		$this->simple_query('COMMIT');
-		return TRUE;
+		return $this->simple_query('COMMIT');
 	}
 
 	// --------------------------------------------------------------------
@@ -168,16 +148,9 @@ class CI_DB_sqlite_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		$this->simple_query('ROLLBACK');
-		return TRUE;
+		return $this->simple_query('ROLLBACK');
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/sqlite3/sqlite3_driver.php b/system/database/drivers/sqlite3/sqlite3_driver.php
index 31e37de91..73e453785 100644
--- a/system/database/drivers/sqlite3/sqlite3_driver.php
+++ b/system/database/drivers/sqlite3/sqlite3_driver.php
@@ -134,22 +134,10 @@ class CI_DB_sqlite3_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		return $this->conn_id->exec('BEGIN TRANSACTION');
 	}
 
@@ -160,14 +148,8 @@ class CI_DB_sqlite3_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return $this->conn_id->exec('END TRANSACTION');
 	}
 
@@ -178,14 +160,8 @@ class CI_DB_sqlite3_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return $this->conn_id->exec('ROLLBACK');
 	}
 
diff --git a/system/database/drivers/sqlsrv/sqlsrv_driver.php b/system/database/drivers/sqlsrv/sqlsrv_driver.php
index 1df3a4258..414669a4b 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_driver.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_driver.php
@@ -197,22 +197,10 @@ class CI_DB_sqlsrv_driver extends CI_DB {
 	/**
 	 * Begin Transaction
 	 *
-	 * @param	bool	$test_mode
 	 * @return	bool
 	 */
-	public function trans_begin($test_mode = FALSE)
+	protected function _trans_begin()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
-		// Reset the transaction failure flag.
-		// If the $test_mode flag is set to TRUE transactions will be rolled back
-		// even if the queries produce a successful result.
-		$this->_trans_failure = ($test_mode === TRUE);
-
 		return sqlsrv_begin_transaction($this->conn_id);
 	}
 
@@ -223,14 +211,8 @@ class CI_DB_sqlsrv_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_commit()
+	protected function _trans_commit()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return sqlsrv_commit($this->conn_id);
 	}
 
@@ -241,14 +223,8 @@ class CI_DB_sqlsrv_driver extends CI_DB {
 	 *
 	 * @return	bool
 	 */
-	public function trans_rollback()
+	protected function _trans_rollback()
 	{
-		// When transactions are nested we only begin/commit/rollback the outermost ones
-		if ( ! $this->trans_enabled OR $this->_trans_depth > 0)
-		{
-			return TRUE;
-		}
-
 		return sqlsrv_rollback($this->conn_id);
 	}
 
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 72bd9acf9..b1caf9b56 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -10,6 +10,7 @@ Release Date: Not Released
 -  Database
 
    -  Optimized :doc:`Database Utility <database/utilities>` method ``csv_from_result()`` for speed with larger result sets.
+   -  Added proper return values to :doc:`Database Transactions <database/transactions>` method ``trans_start()``.
 
 Bug fixes for 3.0.3
 -------------------
@@ -17,6 +18,9 @@ Bug fixes for 3.0.3
 -  Fixed a bug (#4170) - :doc:`Database <database/index>` method ``insert_id()`` could return an identity from the wrong scope with the 'sqlsrv' driver.
 -  Fixed a bug (#4179) - :doc:`Session Library <libraries/sessions>` doesn't properly maintain its state after ID regeneration with the 'database' driver on PHP7.
 -  Fixed a bug (#4173) - :doc:`Database Forge <database/forge>` method ``add_key()`` didn't allow creation of non-PRIMARY composite keys after the "bugfix" for #3968.
+-  Fixed a bug (#4171) - :doc:`Database Transactions <database/transactions>` didn't work with nesting in methods ``trans_begin()``, ``trans_commit()``, ``trans_rollback()``.
+-  Fixed a bug where :doc:`Database Transaction <database/transactions>` methods ``trans_begin()``, ``trans_commit()``, ``trans_rollback()`` ignored failures.
+-  Fixed a bug where all :doc:`Database Transaction <database/transactions>` methods returned TRUE while transactions are actually disabled.
 
 Version 3.0.2
 =============
diff --git a/user_guide_src/source/database/db_driver_reference.rst b/user_guide_src/source/database/db_driver_reference.rst
index ea692515c..8fc26c01b 100644
--- a/user_guide_src/source/database/db_driver_reference.rst
+++ b/user_guide_src/source/database/db_driver_reference.rst
@@ -140,13 +140,15 @@ This article is intended to be a reference for them.
 	.. php:method:: trans_start([$test_mode = FALSE])
 
 		:param	bool	$test_mode: Test mode flag
-		:rtype:	void
+		:returns:	TRUE on success, FALSE on failure
+		:rtype:	bool
 
 		Start a transaction.
 
 	.. php:method:: trans_complete()
 
-		:rtype:	void
+		:returns:	TRUE on success, FALSE on failure
+		:rtype:	bool
 
 		Complete Transaction.