From: Floris Van Nee <florisvannee@Optiver.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
CC: "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>,
        Andres Freund <andres@anarazel.de>
Thread-Topic: [External] Re: error "can only drop stats once" brings down
 database [External]
Thread-Index: AQHaZC2BJX3cZ68Gf0SnR3ukCGL5orGGQZEw
Date: Fri, 3 May 2024 18:10:05 +0000
Message-ID: <8e5cb534706a4f43bd74405c8fd91437@Optiver.com>
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 <215498.1708454947@sss.pgh.pa.us>
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Subject: RE: error "can only drop stats once" brings down database
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=20
> Floris Van Nee <florisvannee@Optiver.com> writes:
> > Hi,
> > On a database we have we've recently seen a fatal error occur twice. Th=
e
> error happened on two different physical replicas (of the same cluster)
> during a WAL redo action in the recovery process. They're running Postgre=
s
> 15.5.
>=20
> > Occurrence 1:
> > 2024-02-01 06:55:54.476 CET,,,70290,,65a29b60.11292,6,,2024-01-13 15:17=
:04
> CET,1/0,0,FATAL,XX000,"can only drop stats once",,,,,"WAL redo at
> A7BD1/D6F9B6C0 for Transaction/COMMIT: 2024-02-01 06:55:54.395851+01;
> ...
>=20
> Hmm.  This must be coming from pgstat_drop_entry_internal.
> I suspect the correct fix is in pgstat_drop_entry, along the lines of
>=20
> -	if (shent)
> +	if (shent && !shent->dropped)
>=20
> but it's not clear to me how the already-dropped case ought to affect the
> function's bool result.  Also, how are we getting into a concurrent-drop
> situation in recovery?

Anyone has further thoughts on this? This still happens occasionally.

-Floris