mysql> explain select count(*) from text,revision where old_flags='utf-8' and rev_id=old_id;
+----+-------------+----------+--------+---------------+---------+---------+--------------------+-----------+-------------+
| id | select_type | table    | type   | possible_keys | key     | key_len | ref                | rows      | Extra       |
+----+-------------+----------+--------+---------------+---------+---------+--------------------+-----------+-------------+
|  1 | SIMPLE      | revision | index  | rev_id        | rev_id  | 4       | NULL               | 114966477 | Using index | 
|  1 | SIMPLE      | text     | eq_ref | PRIMARY       | PRIMARY | 4       | en.revision.rev_id |         1 | Using where |