From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Postgres hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: REINDEX INDEX results in a crash for an index of pg_class since 9.6
Date: Tue, 30 Apr 2019 14:05:50 -0400
Message-ID: <29546.1556647550@sss.pgh.pa.us> (raw)
In-Reply-To: <20190430173457.pg6i6urvevse5jer@alap3.anarazel.de>
References: <20190426020248.iyev66bkpf2abxqd@alap3.anarazel.de>
<7882.1556290296@sss.pgh.pa.us>
<12189.1556575627@sss.pgh.pa.us>
<20190429220924.lfptluzkujb26y2n@alap3.anarazel.de>
<20190430030342.jmbgnih4q3cdoufz@alap3.anarazel.de>
<26051.1556599053@sss.pgh.pa.us>
<BC406D10-146C-4495-AC5E-492CADBFA144@anarazel.de>
<26528.1556599820@sss.pgh.pa.us>
<20190430070552.jzqgcy4ihalx7nur@alap3.anarazel.de>
<30579.1556639470@sss.pgh.pa.us>
<20190430173457.pg6i6urvevse5jer@alap3.anarazel.de>
Andres Freund <andres@anarazel.de> writes:
> It's the lock-upgrade problem I theorized about
> upthread. ReindexIndex(), via RangeVarCallbackForReindexIndex(), takes a
> ShareLock on pg_class, and then goes on to upgrade to RowExclusiveLock
> in RelationSetNewRelfilenode(). But at that time another session
> obviously can already have the ShareLock and would also want to upgrade.
Hmm. Note that this is totally independent of the deadlock mechanism
I reported in my last message on this thread.
I also wonder whether clobber-cache testing would expose cases
we haven't seen that trace to the additional catalog accesses
caused by cache reloads.
> I'm not sure it's worth fixing this.
I am not sure it's even *possible* to fix all these cases. Even
if we could, it's out of scope for v12 let alone the back branches.
I think the only practical solution is to remove those reindex tests.
Even if we ran them in a script with no concurrent scripts, there'd
be risk of failures against autovacuum, I'm afraid. Not often, but
often enough to be annoying.
Possibly we could run them in a TAP test that configures a cluster
with autovac disabled?
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, andres@anarazel.de, michael@paquier.xyz, 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: <29546.1556647550@sss.pgh.pa.us>
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