class DatabaseTransaction

A wrapper class for creating and managing database transactions.

Not all databases or database configurations support transactions. For example, MySQL MyISAM tables do not. It is also easy to begin a transaction and then forget to commit it, which can lead to connection errors when another transaction is started.

This class acts as a wrapper for transactions. To begin a transaction, simply instantiate it. When the object goes out of scope and is destroyed it will automatically commit. It also will check to see if the specified connection supports transactions. If not, it will simply skip any transaction commands, allowing user-space code to proceed normally. The only difference is that rollbacks won't actually do anything.

In the vast majority of cases, you should not instantiate this class directly. Instead, call ->startTransaction(), from the appropriate connection object.

Hierarchy

Expanded class hierarchy of DatabaseTransaction

Related topics

Database abstraction layer
Allow the use of different database servers using the same code base.
1 string reference to 'DatabaseTransaction'
DatabaseConnection::startTransaction in includes/database/database.inc
Returns a new DatabaseTransaction object on this connection.

File

includes/database/database.inc, line 1975

View source 
class DatabaseTransaction {
    
    /**
     * The connection object for this transaction.
     *
     * @var DatabaseConnection
     */
    protected $connection;
    
    /**
     * A boolean value to indicate whether this transaction has been rolled back.
     *
     * @var Boolean
     */
    protected $rolledBack = FALSE;
    
    /**
     * The name of the transaction.
     *
     * This is used to label the transaction savepoint. It will be overridden to
     * 'drupal_transaction' if there is no transaction depth.
     */
    protected $name;
    public function __construct(DatabaseConnection $connection, $name = NULL) {
        $this->connection = $connection;
        // If there is no transaction depth, then no transaction has started. Name
        // the transaction 'drupal_transaction'.
        if (!($depth = $connection->transactionDepth())) {
            $this->name = 'drupal_transaction';
        }
        elseif (!$name) {
            $this->name = 'savepoint_' . $depth;
        }
        else {
            $this->name = $name;
        }
        $this->connection
            ->pushTransaction($this->name);
    }
    public function __destruct() {
        // If we rolled back then the transaction would have already been popped.
        if (!$this->rolledBack) {
            $this->connection
                ->popTransaction($this->name);
        }
    }
    
    /**
     * Retrieves the name of the transaction or savepoint.
     */
    public function name() {
        return $this->name;
    }
    
    /**
     * Rolls back the current transaction.
     *
     * This is just a wrapper method to rollback whatever transaction stack we are
     * currently in, which is managed by the connection object itself. Note that
     * logging (preferable with watchdog_exception()) needs to happen after a
     * transaction has been rolled back or the log messages will be rolled back
     * too.
     *
     * @see DatabaseConnection::rollback()
     * @see watchdog_exception()
     */
    public function rollback() {
        $this->rolledBack = TRUE;
        $this->connection
            ->rollback($this->name);
    }

}

Members

Title Modifiers Object type Summary
DatabaseTransaction::$connection protected property The connection object for this transaction.
DatabaseTransaction::$name protected property The name of the transaction.
DatabaseTransaction::$rolledBack protected property A boolean value to indicate whether this transaction has been rolled back.
DatabaseTransaction::name public function Retrieves the name of the transaction or savepoint.
DatabaseTransaction::rollback public function Rolls back the current transaction.
DatabaseTransaction::__construct public function
DatabaseTransaction::__destruct public function

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