/**
	 * Constructor
	 *
	 * @param 	PDO 	$pdo
	 */
	public function __construct($dsnOrPdo = null, $username = '', $password = '')
	{
		if ($dsnOrPdo instanceof PDO) {
			$this->pdo = $pdo;
			return;
		}
		
		$this->_tablePrefix = self::getDefaultTablePrefix();
		$this->_queryCacheEnabled = self::areQueriesAlwaysCached();
		$this->_resultCacheEnabled = Atomik_Db_Query::areResultsAlwaysCached();
		
		$this->setConnectionInfo($dsnOrPdo, $username, $password);
	}