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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 00:50:20 -0400
Message-ID: <26528.1556599820@sss.pgh.pa.us> (raw)
In-Reply-To: <BC406D10-146C-4495-AC5E-492CADBFA144@anarazel.de>
References: <20190425181648.lgffj43btacmxszu@alap3.anarazel.de>
	<26665.1556218209@sss.pgh.pa.us>
	<20190425195130.hhdp5tcpapnupszq@alap3.anarazel.de>
	<29295.1556222523@sss.pgh.pa.us>
	<20190425210309.cnofpjnwsrhdnahd@alap3.anarazel.de>
	<31933.1556226753@sss.pgh.pa.us>
	<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>

Andres Freund <andres@anarazel.de> writes:
> On April 29, 2019 9:37:33 PM PDT, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Seems like putting reindexes of pg_class into a test script that runs
>> in parallel with other DDL wasn't a hot idea.

> Saw that. Will try to reproduce (and if necessary either run separately or revert). But isn't that somewhat broken? They're not run in a transaction, so the locking shouldn't be deadlock prone.

Hm?  REINDEX INDEX is deadlock-prone by definition, because it starts
by opening/locking the index and then it has to open/lock the index's
table.  Every other operation locks tables before their indexes.

			regards, tom lane





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