On Sun, Mar 21, 2021 at 03:22:00PM -0300, Alvaro Herrera wrote: > On 2021-Mar-21, Justin Pryzby wrote: > > > On Sun, Mar 21, 2021 at 03:01:15PM -0300, Alvaro Herrera wrote: > > > > But note that it doesn't check if an existing constraint "implies" the > > > > new > > > > constraint - maybe it should. > > > > > > Hm, I'm not sure I want to do that, because that means that if I later > > > have to attach the partition again with the same partition bounds, then > > > I might have to incur a scan to recheck the constraint. I think we want > > > to make the new constraint be as tight as possible ... > > > > The ATTACH PARTITION checks if any existing constraint impilies the > > (proposed) > > partition bounds, not just if constraints are equal. So I'm suggesting to > > do > > the same here. > > So if we do that on DETACH, what would happen on ATTACH?
Do you mean what happens to the constraint that was already there ? Nothing, since it's not ours to mess with. Checking ImpliedBy() rather than equal() doesn't change that. I proposed this a few years ago for DETACH (without concurrently), specifically to avoid the partition scans. https://www.postgresql.org/message-id/20180601221428.gu5...@telsasoft.com |The docs say: if detaching/re-attach a partition, should first ADD CHECK to |avoid a slow ATTACH operation. Perhaps DETACHing a partition could |implicitly CREATE a constraint which is usable when reATTACHing? -- Justin
