This table has not being read/written for months now (deprecated in favor of change_tag_def.ctd_user_defined), it has been dropped from the code as well.
- SQL to run: DROP TABLE valid_tag (https://gerrit.wikimedia.org/r/#/c/479266/)
- Where to run those changes: all.dblist
- When to run those changes: any time would work
- If the schema change is backwards compatible: No.
- If the schema change has been tested already on some of the test/beta wikis: Tested in beta cluster
- if the data should be made available on the labs replicas and/or dumps: No