Feedback-ID: i0fe9450f:Fastmail
Date: Fri, 27 May 2022 08:53:03 +0900
From: Michael Paquier <michael@paquier.xyz>
To: "Imseih (AWS), Sami" <simseih@amazon.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: [BUG] Panic due to incorrect missingContrecPtr after promotion
Message-ID: <YpAS32GHmbsRLXbS@paquier.xyz>
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On Tue, Feb 22, 2022 at 07:20:55PM +0000, Imseih (AWS), Sami wrote:
> The overwrite_contrecord was introduced in 13.5 with https://git.postgres=
ql.org/gitweb/?p=3Dpostgresql.git;a=3Dcommit;h=3Dff9f111bce24.
>=20
> Attached is a patch and a TAP test to handle this condition. The
> patch ensures that an overwrite_contrecord is only created if the
> missingContrecPtr is ahead of the last wal record.

The test you are introducing to force a complete segment to be filled
is funky, and kind of nice actually while being cheap.  This part
particularly makes the test predictable:
++unlink $node->basedir . "/pgdata/pg_wal/$endfile"
++  or die "could not unlink " . $node->basedir
=2E "/pgdata/pg_wal/$endfile: $!";

I really like that.

> With the patch, running the same tap test succeeds and a PANIC is
> not observed.

This needs a very close lookup, I'll try to check all that except if
somebody beats me to it.
--
Michael

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