[14:35:30] <Amir1>	 87 indexes to sift through and figure out if they are really needed or not (T342697). I want to cry.
[14:35:31] <stashbot>	 T342697: Audit of unused indexes, 2023 - https://phabricator.wikimedia.org/T342697
[15:35:43] <Krinkle>	 Amir1: Can you elaborate on what it means for an index to be reported as unused by this admin query, but still "needed"? Does this admin query only count cases of forced index, or only queries in the last few minutes? If not, what kind of scenario is it missing?
[15:37:56] <Amir1>	 the report is saying that index for that specific wiki has not been used in that replica since the replica was started. It can be needed in a feature or a code path that's not enable for that wiki, in some cases it can be used so rarely that the index is not showing up in that replica since mariadb being started (=a couple of weeks), it can be not used in that specific wiki, etc.
[15:43:54] <Krinkle>	 Amir1: ah I see, so if we'd intersect that with the same query run for diverse handful of wikis, and maybe 3-4 different replicas; that might exclude the bulk of false positives.
[15:56:52] <Amir1>	 yeah, I should do that
[16:51:24] <Lucas_WMDE>	 some of those indexes also sounded to me like they might only be used on a primary
[16:54:51] <Lucas_WMDE>	 e.g. comment_hash
[16:55:08] <Lucas_WMDE>	 (though I’m not actually sure why CommentStore doesn’t first try to find the comment by its hash on a replica)