Yes, I've seen this before when I've killed (or otherwise crashed) a migration in process; migrate_tmp doesn't get automatically cleaned up -- and, to allow for recovery, probably shouldn't.    Any idea what may have caused it in your case?For a development database I've most commonly just deleted the migrate_tmp table manually and rerun the migration.  It's worth noting that *only* sqlite can have this problem, due to the way migrations work.

-Dannon