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From: Antonin Houska <ah@cybertec.at>
To: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>
Cc: Noah Misch <noah@leadboat.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: vignesh C <vignesh21@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Robert Treat <rob@xzilla.net>
Subject: Re: Adding REPACK [concurrently]
Date: Tue, 07 Apr 2026 10:57:46 +0200
Message-ID: <188275.1775552266@localhost> (raw)
In-Reply-To: <CAFC+b6ojcdgpVb0euBvqy-b3W7F=NXZ7PhrruQnyzkDouoGZXQ@mail.gmail.com>
References: <CALDaNm3tiKhtegx5Cawi34UjbHmNGEDNAtScGM1RgWRtV-5_0Q@mail.gmail.com>
	<202604060918.qw5ms7cbr2hz@alvherre.pgsql>
	<pbqm52nsviwojptiszg2g6pqntbhnhaotbxshiysnensshnuv5@v6pmney4jror>
	<20260407011056.50.noahmisch@microsoft.com>
	<jaxapcek2yxbpyegajeim4aczdkjo4od7xxmtauf4fqtjtcpph@ws4anpqvjero>
	<1976915.1775537087@sss.pgh.pa.us>
	<CAFC+b6ojcdgpVb0euBvqy-b3W7F=NXZ7PhrruQnyzkDouoGZXQ@mail.gmail.com>

Srinath Reddy Sadipiralla <srinath2133@gmail.com> wrote:

> Hi Tom,
> 
> On Tue, Apr 7, 2026 at 10:14 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 
>  Maybe you saw this already, but BF member skink is failing on
>  src/test/modules/injection_points/specs/repack.spec:
> 
>  https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2026-04-06%2022%3A50%3A41
> 
> i looked into this , it seems like valgrind catches the uninitialised padding bytes, which
> repack worker is writing using BufFileWrite, it seems this fix solved the problem.
> 
> diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
> index 2e6197f5f35..f5682b87626 100644
> --- a/src/backend/utils/time/snapmgr.c
> +++ b/src/backend/utils/time/snapmgr.c
> @@ -1739,6 +1739,8 @@ SerializeSnapshot(Snapshot snapshot, char *start_address)
>  
>   Assert(snapshot->subxcnt >= 0);
>  
> + MemSet(&serialized_snapshot, 0, sizeof(SerializedSnapshotData));
> +
>   /* Copy all required fields */
>   serialized_snapshot.xmin = snapshot->xmin;
>   serialized_snapshot.xmax = snapshot->xmax;
> 
> thoughts?

Could you reproduce the failure in your environment?

I haven't thought of this explanation because BufFileWrite() only copies the
data to a buffer in the BufFile structure and BufFileDumpBuffer() writes the
buffer. Maybe valgrind is able to track the copying?

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com





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  Cc: ah@cybertec.at, srinath2133@gmail.com, tgl@sss.pgh.pa.us, andres@anarazel.de, noah@leadboat.com, alvherre@alvh.no-ip.org, vignesh21@gmail.com, amit.kapila16@gmail.com, mihailnikalayeu@gmail.com, boekewurm+postgres@gmail.com, pgsql-hackers@lists.postgresql.org, rob@xzilla.net
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