+----+-------------+----------+-------+---------------+--------+---------+------+-----------+--------------------------+
| id | select_type | table    | type  | possible_keys | key    | key_len | ref  | rows      | Extra                    |
+----+-------------+----------+-------+---------------+--------+---------+------+-----------+--------------------------+
|  1 | SIMPLE      | activity | index | parent        | parent | 9       | NULL | 113020037 | Using where; Using index |
+----+-------------+----------+-------+---------------+--------+---------+------+-----------+--------------------------+
1 row in set (0.48 sec)

+----+-------------+----------+-------+---------------+--------+---------+------+------+--------------------------+
| id | select_type | table    | type  | possible_keys | key    | key_len | ref  | rows | Extra                    |
+----+-------------+----------+-------+---------------+--------+---------+------+------+--------------------------+
|  1 | SIMPLE      | activity | range | parent        | parent | 9       | NULL | 7933 | Using where; Using index |
+----+-------------+----------+-------+---------------+--------+---------+------+------+--------------------------+
1 row in set (0.56 sec)