From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
cc: pgsql-hackers@lists.postgresql.org
Subject: Re: pgsql: autovacuum: handle analyze for partitioned tables
In-reply-to: <20210408183551.GA16359@alvherre.pgsql>
References: <20210408183551.GA16359@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@alvh.no-ip.org>
	message dated "Thu, 08 Apr 2021 14:35:51 -0400"
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Date: Thu, 08 Apr 2021 14:47:01 -0400
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Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> On 2021-Apr-08, Tom Lane wrote:
>> Yeah.  I hit this on another machine that isn't using EXEC_BACKEND,
>> and I concur it looks more like a race condition.  I think the problem
>> is that autovacuum is calling find_all_inheritors() on a relation it
>> has no lock on, contrary to that function's API spec.

> Hmm.  Autovacuum tries hard to avoid grabbing locks on relations until
> really needed (at vacuum/analyze time), which is why all these tests
> only use data that can be found in the pg_class rows and pgstat entries.

Yeah, I was worried about that.

> So I tend to think that my initial instinct was the better direction: we
> should not be doing any find_all_inheritors() here at all, but instead
> rely on pg_class.reltuples to be set for the partitioned table.

+1

			regards, tom lane