Comment 2 for bug 1380983

An error occurred while upgrading the database:
 │
 │ mysql said: ERROR 1091 (42000) at line 3: Can't DROP 'cache_id'; check
 │ that column/key exists
 │
 │ Fortunately, /var/cache/dbconfig-common/backups/roundcube_0.7.1-2.mysql
 │ holds a backup of the database, made just before the upgrade.
 │
 │ If at this point you choose "retry", you will be prompted with all the
 │ configuration questions once more and another attempt will be made at
 │ performing the operation. "retry (skip questions)" will immediately
 │ attempt the operation again, skipping all questions. If you choose
 │ "abort", the operation will fail and you will need to downgrade,
 │ reinstall, reconfigure this package, or otherwise manually intervene to
 │

This is on do-release-upgrade from 12.04 to 14.04.