From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: ALTER TABLE .. DETACH PARTITION CONCURRENTLY
Date: Wed, 23 Sep 2020 12:23:21 -0300
Message-ID: <20200923152321.GA26342@alvherre.pgsql> (raw)
In-Reply-To: <CA+HiwqEJLdJkyxg4RP9YS3eBzxHJ9kzdUnmqrA=9tL19qM7wXg@mail.gmail.com>
On 2020-Sep-23, Amit Langote wrote:
Hi Amit, thanks for reviewing this patch!
> On Tue, Aug 4, 2020 at 8:49 AM Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> I suspect that we don't really need this defensive constraint. I mean
> even after committing the 1st transaction, the partition being
> detached still has relispartition set to true and
> RelationGetPartitionQual() still returns the partition constraint, so
> it seems the constraint being added above is duplicative.
Ah, thanks for thinking through that. I had vague thoughts about this
being unnecessary in the current mechanics, but hadn't fully
materialized the thought. (The patch was completely different a few
unposted iterations ago).
> Moreover, the constraint is not removed as part of any cleaning up
> after the DETACH process, so repeated attach/detach of the same
> partition results in the constraints piling up:
Yeah, I knew about this issue (mentioned in my self-reply on Aug 4) and
didn't worry too much about it because I was thinking I'd rather get rid
of the constraint addition in the first place.
> Noticed a bug/typo in the patched RelationBuildPartitionDesc():
>
> - inhoids = find_inheritance_children(RelationGetRelid(rel), NoLock);
> + inhoids = find_inheritance_children(RelationGetRelid(rel), NoLock,
> + include_detached);
>
> You're passing NoLock for include_detached which means you never
> actually end up including detached partitions from here.
I fixed this in the version I posted on Sept 10. I think you were
reading the version posted at the start of this thread.
Thanks,
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: alvherre@2ndquadrant.com, amitlangote09@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: ALTER TABLE .. DETACH PARTITION CONCURRENTLY
In-Reply-To: <20200923152321.GA26342@alvherre.pgsql>
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