num_rows in pear db

I have global $db object, for some reason the db->num_rows object doesnt reset with each query and it is storing $num_rows for each query and my program is dumping core because this object is too large: [db] => db_mysql Object

        (
            [connection] => Resource id #29
            [phptype] => mysql
            [dbsyntax] => mysql
            [prepare_tokens] => Array
                (
                )

            [prepare_types] => Array
                (
                )

            [num_rows] => Array
                (
                    [33] => 3
                    [35] => 1
                    [36] => 1
                    [41] => 0
                    [42] => 0
                    [43] => 1
                    [44] => 1
                       ..
                    [476162] => 1

How do I reset this $db object num_rows?