While troubleshooting {T223952} I noticed the following slow query on enwiki (we don't know if it is related, but it needs fixing anyways, hence this task)
Note the explain and then the real execution plan
{P8550}
The query takes around 8 seconds to run:
```
2 rows in set (8.43 sec)
```
That query arriving to the three enwiki API DBs (as expected): db1080, db1118,db1119
When using `page_timestamp` index, the query flies:
```
root@db1134.eqiad.wmnet[enwiki]> explain SELECT /* ApiQueryRevisions::run */ rev_id, rev_page, rev_timestamp, rev_minor_edit, rev_deleted, rev_len, rev_parent_id, rev_sha1, comment_rev_comment.comment_text AS `rev_comment_text`, comment_rev_comment.comment_data AS `rev_comment_data`, comment_rev_comment.comment_id AS `rev_comment_cid`, actor_rev_user.actor_user AS `rev_user`, actor_rev_user.actor_name AS `rev_user_text`, temp_rev_user.revactor_actor AS `rev_actor`, page_namespace, page_title, page_id, page_latest, page_is_redirect, page_len, user_name FROM `revision` JOIN `revision_comment_temp` `temp_rev_comment` ON ((temp_rev_comment.revcomment_rev = rev_id)) JOIN `comment` `comment_rev_comment` ON ((comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id)) JOIN `revision_actor_temp` `temp_rev_user` ON ((temp_rev_user.revactor_rev = rev_id)) JOIN `actor` `actor_rev_user` ON ((actor_rev_user.actor_id = temp_rev_user.revactor_actor)) JOIN `page` ON ((page_id = rev_page)) LEFT JOIN `user` ON ((actor_rev_user.actor_user != 0) AND (user_id = actor_rev_user.actor_user)) WHERE rev_page = '35159700' ORDER BY rev_timestamp DESC, rev_id DESC LIMIT 2 /* d4b1615c1ca7cc6e58b19616c200b731 db1118 enwiki 4s */;
+------+-------------+---------------------+--------+--------------------------------------------------------+----------------+---------+-----------------------------------------------+--------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+---------------------+--------+--------------------------------------------------------+----------------+---------+-----------------------------------------------+--------+-------------+
| 1 | SIMPLE | revision | ref | PRIMARY,page_timestamp,page_user_timestamp,rev_page_id | page_timestamp | 4 | const | 151648 | Using where |
| 1 | SIMPLE | page | eq_ref | PRIMARY | PRIMARY | 4 | enwiki.revision.rev_page | 1 | |
| 1 | SIMPLE | temp_rev_comment | ref | PRIMARY,revcomment_rev | PRIMARY | 4 | enwiki.revision.rev_id | 1 | Using index |
| 1 | SIMPLE | comment_rev_comment | eq_ref | PRIMARY | PRIMARY | 8 | enwiki.temp_rev_comment.revcomment_comment_id | 1 | |
| 1 | SIMPLE | temp_rev_user | ref | PRIMARY,revactor_rev,actor_timestamp | PRIMARY | 4 | enwiki.revision.rev_id | 1 | Using index |
| 1 | SIMPLE | actor_rev_user | eq_ref | PRIMARY | PRIMARY | 8 | enwiki.temp_rev_user.revactor_actor | 1 | |
| 1 | SIMPLE | user | eq_ref | PRIMARY | PRIMARY | 4 | enwiki.actor_rev_user.actor_user | 1 | Using where |
+------+-------------+---------------------+--------+--------------------------------------------------------+----------------+---------+-----------------------------------------------+--------+-------------+
7 rows in set (0.00 sec)
```
```
root@db1134.eqiad.wmnet[enwiki]> SELECT /* ApiQueryRevisions::run */ rev_id, rev_page.....snipped
2 rows in set (0.00 sec)
```