protected function _process( $stmts )
	{
		$this->_msg( 'Adding unique constraints to catalog index tables', 0 );
		$this->_status( '' );

		foreach( $stmts as $table => $list )
		{
			foreach( $list as $index => $sqls )
			{
				$this->_msg( sprintf( 'Checking index "%1$s"', $index ), 1 );

				if( $this->_schema->tableExists( $table ) === true
					&& $this->_schema->constraintExists( $table, $index ) === false )
				{
					$this->_executeList( $sqls );
					$this->_status( 'added' );
				}
				else
				{
					$this->_status( 'OK' );
				}
			}
		}
	}