[openstack-dev] [oslo.db] Proposal: Get rid of deleted column
ed at openstack.org
Tue Aug 20 19:51:39 UTC 2013
On Aug 20, 2013, at 2:33 PM, Chris Behrens <cbehrens at codestud.com>
> For instances table, we want to make sure 'uuid' is unique. But we can't put a unique constraint on that alone. If that instance gets deleted.. we should be able to create another entry with the same uuid without a problem. So we need a unique constraint on uuid+deleted. But if 'deleted' is only 0 or 1… we can only have 1 entry deleted and 1 entry not deleted. Using deleted=`id` to mark deletion solves that problem. You could use deleted_at… but 2 creates and deletes within the same second would not work. :)
This creates another problem if you ever need to delete this second instance, because now you have two with the same uuid and the same deleted status. 'deleted_at' is slightly better, as the only place it would fail is if all of this happened within the same unit of precision for that time value.
-- Ed Leafe
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