From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
---|---|
To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
Cc: | Amit Langote <amitlangote09(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: ALTER TABLE .. DETACH PARTITION CONCURRENTLY |
Date: | 2021-03-21 19:07:12 |
Message-ID: | 20210321190712.GA8502@alvherre.pgsql |
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Lists: | pgsql-hackers |
On 2021-Mar-21, Justin Pryzby wrote:
> On Sun, Mar 21, 2021 at 03:22:00PM -0300, Alvaro Herrera wrote:
>
> > 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.
No, I meant what happens regarding checking existing values in the
table: is the table scanned even if the partition constraint is implied
by existing table constraints?
> I proposed this a few years ago for DETACH (without concurrently), specifically
> to avoid the partition scans.
> https://www.postgresql.org/message-id/20180601221428.GU5164@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?
Well, I agree with you that we should add such a constraint.
--
Álvaro Herrera Valdivia, Chile
"The problem with the future is that it keeps turning into the present"
(Hobbes)
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