On Mar 7, 2019, at 9:13 AM, Brooke Storm <bstorm@wikimedia.org> wrote:

Since the MCR refactor of the Mediawiki database schema has been progressing (https://phabricator.wikimedia.org/T166733 and many other tickets), one of the last steps is dropping the columns from the wiki replica schema.

The column drops are being tracked and are explained well here https://phabricator.wikimedia.org/T212972, and currently the change is ready to be applied.  It is already applied to two wikis (eswiki and huwiki since there was a column problem that needed fixing).  The tables with names such as <tablename>_compat will retain a similar structure if that is needed for refactoring.

From the ticket, this is a summary of what is changing, organized by table name:

• archive: Remove ar_comment
• archive_userindex: Remove ar_comment
• filearchive:
  • Remove fa_deleted_reason
  • Remove fa_description
• filearchive_userindex:
  • Remove fa_deleted_reason
  • Remove fa_description
• image: Remove img_description
• ipblocks: Remove ipb_reason.
• ipblocks_ipindex: Remove ipb_reason.
• logging: Remove log_comment.
• logging_logindex: Remove log_comment.
• logging_userindex: Remove log_comment.
• oldimage: Remove oi_description
• oldimage_userindex: Remove oi_description
• recentchanges: Remove rc_comment.
• recentchanges_userindex: Remove rc_comment.
• revision: Remove rev_comment.
• revision_userindex: Remove rev_comment.

The changes to the _compat tables should not affect anything.

We will deploy the change early next week (Tuesday - 3/12/2019).  In most cases, if a table isn’t working for your tool or app anymore because of the change, you can switch to a table named $tablename_compat and it will appear to have the same schema, but it is recommended that comment references use a join to the new comment table on a “comment_id” field instead where possible.

Brooke Storm

Operations Engineer

Wikimedia Cloud Services

bstorm@wikimedia.org

IRC: bstorm_