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From: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Date: Tue, 7 Apr 2026 14:12:22 +0530
Message-ID: 
 <CAFC+b6ojcdgpVb0euBvqy-b3W7F=NXZ7PhrruQnyzkDouoGZXQ@mail.gmail.com>
Subject: Re: Adding REPACK [concurrently]
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, Noah Misch <noah@leadboat.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>, vignesh C <vignesh21@gmail.com>,
	Antonin Houska <ah@cybertec.at>, Amit Kapila <amit.kapila16@gmail.com>,
	Mihail Nikalayeu <mihailnikalayeu@gmail.com>,
	Matthias van de Meent <boekewurm+postgres@gmail.com>,
	Pg Hackers <pgsql-hackers@lists.postgresql.org>,
 Robert Treat <rob@xzilla.net>
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Hi Tom,

On Tue, Apr 7, 2026 at 10:14=E2=80=AFAM 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=3Dskink&dt=3D2026=
-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 >=3D 0);

+ MemSet(&serialized_snapshot, 0, sizeof(SerializedSnapshotData));
+
  /* Copy all required fields */
  serialized_snapshot.xmin =3D snapshot->xmin;
  serialized_snapshot.xmax =3D snapshot->xmax;

thoughts?


--=20
Thanks,
Srinath Reddy Sadipiralla
EDB: https://www.enterprisedb.com/

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<div dir=3D"ltr"><div dir=3D"ltr">Hi Tom,</div><br><div class=3D"gmail_quot=
e gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, Apr =
7, 2026 at 10:14=E2=80=AFAM Tom Lane &lt;<a href=3D"mailto:tgl@sss.pgh.pa.u=
s">tgl@sss.pgh.pa.us</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quo=
te" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204=
);padding-left:1ex">Maybe you saw this already, but BF member skink is fail=
ing on<br>
src/test/modules/injection_points/specs/repack.spec:<br>
<br>
<a href=3D"https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=3Dskink&=
amp;dt=3D2026-04-06%2022%3A50%3A41" rel=3D"noreferrer" target=3D"_blank">ht=
tps://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=3Dskink&amp;dt=3D2026=
-04-06%2022%3A50%3A41</a><br>
</blockquote></div><div><br>i looked into this , it seems like valgrind cat=
ches the=C2=A0uninitialised padding bytes, which<br>repack worker is writin=
g using=C2=A0BufFileWrite, it seems this fix solved the problem.<br><br>dif=
f --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr=
.c<br>index 2e6197f5f35..f5682b87626 100644<br>--- a/src/backend/utils/time=
/snapmgr.c<br>+++ b/src/backend/utils/time/snapmgr.c<br>@@ -1739,6 +1739,8 =
@@ SerializeSnapshot(Snapshot snapshot, char *start_address)<br>=C2=A0<br>=
=C2=A0	Assert(snapshot-&gt;subxcnt &gt;=3D 0);<br>=C2=A0<br>+	MemSet(&amp;s=
erialized_snapshot, 0, sizeof(SerializedSnapshotData));<br>+<br>=C2=A0	/* C=
opy all required fields */<br>=C2=A0	serialized_snapshot.xmin =3D snapshot-=
&gt;xmin;<br>=C2=A0	serialized_snapshot.xmax =3D snapshot-&gt;xmax;<br><br>=
thoughts?</div><div>=C2=A0</div><div><br></div><span class=3D"gmail_signatu=
re_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signature"><div di=
r=3D"ltr"><span style=3D"color:rgb(34,34,34)">Thanks,</span><br style=3D"co=
lor:rgb(34,34,34)"><span style=3D"color:rgb(34,34,34)">Srinath Reddy Sadipi=
ralla</span><br style=3D"color:rgb(34,34,34)"><span style=3D"color:rgb(34,3=
4,34)">EDB:=C2=A0</span><a href=3D"https://www.enterprisedb.com/" style=3D"=
color:rgb(17,85,204)" target=3D"_blank">https://www.enterprisedb.com/</a></=
div></div></div>

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