In rECHUd24e689913dc341d0b82aaa41d375b8ca1e4ff32 the columns 'cul_reason_id' and 'cul_reason_plaintext_id' were added so that the reason for the check would use the comment table. A config is pinned on WMF wikis with the schema migration value of reading and writing to old in rOMWCa454d3bc56c344fa62625f7c292ea087bddfebe5. Currently no code in CheckUser attempts to write or read from these columns. https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/820835 is waiting for review and would write to these columns if the schema config variable allowed it.
- ALTERs to run: https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/CheckUser/+/4ed2e7953890e0823c67e392876f2e132f8e6959/schema/mysql/patch-cu_log-comment_table_for_reason.sql
- Where to run those changes: all
- When to run those changes: At any time
- If the schema change is backwards compatible: Yes.
- If the schema change has been tested already on some of the test/beta wikis: Has been merged for a few months and changes were in release 1.39. CheckUser is not on beta cluster.
- if the data should be made available on the labs replicas and/or dumps: Everything is private