From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Michael Paquier <michael@paquier.xyz>,
        Postgres hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: REINDEX INDEX results in a crash for an index of pg_class since
 9.6
In-reply-to: <20190502021913.axyvyyyw5547swy5@alap3.anarazel.de>
References: <28926.1556664156@sss.pgh.pa.us>
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 <20190501172115.4cvz3rp6np43odut@alap3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Wed, 01 May 2019 19:19:13 -0700"
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Date: Thu, 02 May 2019 10:49:00 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2019-05-01 22:01:53 -0400, Tom Lane wrote:
>> I think that argument is pretty pointless considering that "REINDEX TABLE
>> pg_class" does it this way, and that code is nearly old enough to
>> vote.

> IMO the reindex_relation() case isn't comparable.

IMV it's the exact same case: we need to perform a pg_class update while
one or more of pg_class's indexes shouldn't be touched.  I am kind of
wondering why it didn't seem to be necessary to cover this for REINDEX
INDEX back in 2003, but it clearly is necessary now.

> That's not pretty either :(

So, I don't like your patch, you don't like mine.  Anybody else
want to weigh in?

We do not have the luxury of time to argue about this.  If we commit
something today, we *might* get a useful set of CLOBBER_CACHE_ALWAYS
results for all branches by Sunday.  Those regression tests will have to
come out of the back branches on Sunday, because we are not shipping minor
releases with unstable regression tests, and I've heard no proposal for
avoiding the occasional-deadlock problem.

			regards, tom lane