protected function _getCachedStatement( MW_DB_Connection_Interface $conn, $key, $sql = null )
	{
		if( !isset( $this->_stmts['stmt'][$key] ) || !isset( $this->_stmts['conn'][$key] ) || $conn !== $this->_stmts['conn'][$key] )
		{
			if( $sql === null ) {
				$sql = $this->_context->getConfig()->get( $key, $key );
			}

			$this->_stmts['stmt'][$key] = $conn->create( $sql );
			$this->_stmts['conn'][$key] = $conn;
		}

		return $this->_stmts['stmt'][$key];
	}