Summary:
See T13193. See T13077. If we drop a column which is part of a UNIQUE KEY, MariaDB raises an error.
This is probably a bad idea on our side anyway, but in this case it wasn't an obviously bad idea.
To get around this:
- Drop the unique key, if it exists, before dropping the column.
- Explicitly add the new unique key afterward.
Test Plan: Ran `bin/storage upgrade` locally without issue, but I'm on MySQL. Will follow up on T13193.
Reviewers: amckinley
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Differential Revision: https://secure.phabricator.com/D19624
