2009/3/25 Brion Vibber brion@wikimedia.org:
David Gerard wrote:
The "usermerge" procedure is presently irreversible. Are there plans for a way to make it reversible in case of error? I'm assuming error (and a great deal of tedious mucking about to go back) is inevitable, since the action is taken by humans.
I assume this is about the UserMerge extension? (Note we're not currently using this at Wikimedia.)
It would probably be tricky to implement, but not impossible. Basically would need to record which revisions, log entries, etc got reassigned (potentially many tens of thousands in a single merge event) and their original assignment.
An extra column in any table with a "user id" column for "original user id" (which would be identical to user id for the vast majority of rows) would be sufficient for most unmerges. There would still be a problem if an account was involved in more than one merge, though.