The high-level checklist:
- 0. Set the configuration flag to "old" (see T166732) (not needed, default is now "old")
- 1. Merge the first patch for T166732: Refactor comment storage in the database and abstract access in MediaWiki (adding new schemas and code)
- 2. Perform schema change (T174569)
- 3. Turn the feature flag to "read+write both". See if stuff breaks.
- 3.1. Announce the pending change to wikitech-l@ and cloud@, and give time for people to update.
- 3.2. Make sure all deployed extensions are updated.
- 4. Turn the feature flag to "write new only, read both". See if stuff breaks.
- 5. Run the maintenance script(s) to migrate all the old stuff to new stuff, blanking the old stuff in the process.
- 6. Turn the feature flag to "new only".
- Default and CI
- Beta Cluster
- Group 0
- Group 1
- Group 2
- 7. Remove old schemas and code
- 7.1. Update WMCS replicas to no longer reference old schemas (T212972).
- 7.2. Write and merge patches to remove $wgCommentTableSchemaMigrationStage, supporting code, and old schemas.
- 7.3. Submit Schema-change task for WMF production (T233135).
For the cleaning up of revision_comment_temp, see T215466. This and T188327 both block T161671, which in turn is the first step of that task.