While troubleshooting T205904 we found that there is a patch that was merged 9 years ago but never got deployed in production: https://github.com/wikimedia/mediawiki/blob/master/maintenance/archives/patch-change_tag-indexes.sql
That touches a few things, but for now, we are going to focus on the `change_tag` table as we are doing some work already with it: T203709
The following indexes are now redudant:
```
UNIQUE KEY `ct_rc_id` (`ct_rc_id`,`ct_tag`),
UNIQUE KEY `ct_log_id` (`ct_log_id`,`ct_tag`),
UNIQUE KEY `ct_rev_id` (`ct_rev_id`,`ct_tag`),
KEY `change_tag_rc_tag_nonuniq` (`ct_rc_id`,`ct_tag`),
KEY `change_tag_log_tag_nonuniq` (`ct_log_id`,`ct_tag`),
KEY `change_tag_rev_tag_nonuniq` (`ct_rev_id`,`ct_tag`)
```
So we need to drop them:
```
DROP INDEX ct_rc_id ON /*_*/change_tag;
DROP INDEX ct_log_id ON /*_*/change_tag;
DROP INDEX ct_rev_id ON /*_*/change_tag;
```
`ct_tag` doesn't exist, so maybe that one was deployed. Who knows what happened 9 years ago.
This needs to be dropped in eqiad first, and once we are back in eqiad, finish it on codfw:
s1
[] eqiad
[] codfw
s2
[] eqiad
[] codfw
s3
[] eqiad
[] codfw
s4
[] eqiad
[] codfw
s5
[] eqiad
[] codfw
s6
[] eqiad
[] codfw
s7
[] eqiad
[] codfw
s8
[] eqiad
[] codfw
labs
[] labswiki
[] labstestwiki