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 <CAHg+QDeoccU5CudrJpmSKZfKZ1gRMNY=5BxSC=JpHgkonzgcOw@mail.gmail.com>
 <187781.1777902048@sss.pgh.pa.us>
In-Reply-To: <187781.1777902048@sss.pgh.pa.us>
From: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Date: Mon, 4 May 2026 07:26:34 -0700
Message-ID: 
 <CAHg+QDeteXPbPFsThTGTL=qp4dgiP1AH1kKktifcksDbiaRROw@mail.gmail.com>
Subject: Re: [Bug]Vacuum full silently NULL out fast default columns
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	=?UTF-8?Q?=C3=81lvaro_Herrera?= <alvherre@kurilemu.de>,
	Antonin Houska <ah@cybertec.at>
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Hi,

On Mon, May 4, 2026 at 6:40=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> writes:
> > VACUUM FULL silently turns columns added via ALTER TABLE ... ADD COLUMN
> ...
> > DEFAULT <const> into NULL
> > on all pre-existing rows. The issue exists for other operations like
> > CLUSTER, REPACK.
>
> That is a seriously awful bug.  Fortunately it is not in any shipping
> release.  A quick bisect run agrees that it broke here:
>
> 28d534e2ae0ac888b5460f977a10cd9bb017ef98 is the first bad commit
> commit 28d534e2ae0ac888b5460f977a10cd9bb017ef98 (HEAD)
> Author: =C3=81lvaro Herrera <alvherre@kurilemu.de>
> Date:   Mon Apr 6 21:55:08 2026 +0200
>
>     Add CONCURRENTLY option to REPACK
>
> > Patch attached. Added a regression test in fast_default.sql covering
> > VACUUM FULL, CLUSTER, and REPACK on a table with fast-default columns
> > including a NOT NULL CHECK column.
>
> I don't know if this is the best code fix (I don't like putting extra
> checks into a loop condition like this).  But I agree we need some
> more tests covering this area.
>
Thanks for reviewing! Attached v2 patch. Agreed, tried to optimize LOC in
V1. Before the change
loop was not breaking early, I fixed that as well in V2.

Thanks,
Satya

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<div dir=3D"ltr"><div dir=3D"ltr">Hi,</div><br><div class=3D"gmail_quote gm=
ail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Mon, May 4, 2=
026 at 6:40=E2=80=AFAM Tom Lane &lt;<a href=3D"mailto:tgl@sss.pgh.pa.us">tg=
l@sss.pgh.pa.us</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" s=
tyle=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);pad=
ding-left:1ex">SATYANARAYANA NARLAPURAM &lt;<a href=3D"mailto:satyanarlapur=
am@gmail.com" target=3D"_blank">satyanarlapuram@gmail.com</a>&gt; writes:<b=
r>
&gt; VACUUM FULL silently turns columns added via ALTER TABLE ... ADD COLUM=
N ...<br>
&gt; DEFAULT &lt;const&gt; into NULL<br>
&gt; on all pre-existing rows. The issue exists for other operations like<b=
r>
&gt; CLUSTER, REPACK.<br>
<br>
That is a seriously awful bug.=C2=A0 Fortunately it is not in any shipping<=
br>
release.=C2=A0 A quick bisect run agrees that it broke here:<br>
<br>
28d534e2ae0ac888b5460f977a10cd9bb017ef98 is the first bad commit<br>
commit 28d534e2ae0ac888b5460f977a10cd9bb017ef98 (HEAD)<br>
Author: =C3=81lvaro Herrera &lt;<a href=3D"mailto:alvherre@kurilemu.de" tar=
get=3D"_blank">alvherre@kurilemu.de</a>&gt;<br>
Date:=C2=A0 =C2=A0Mon Apr 6 21:55:08 2026 +0200<br>
<br>
=C2=A0 =C2=A0 Add CONCURRENTLY option to REPACK<br>
<br>
&gt; Patch attached. Added a regression test in fast_default.sql covering<b=
r>
&gt; VACUUM FULL, CLUSTER, and REPACK on a table with fast-default columns<=
br>
&gt; including a NOT NULL CHECK column.<br>
<br>
I don&#39;t know if this is the best code fix (I don&#39;t like putting ext=
ra<br>
checks into a loop condition like this).=C2=A0 But I agree we need some<br>
more tests covering this area.<br></blockquote><div>Thanks for reviewing! A=
ttached v2 patch. Agreed, tried to optimize LOC in V1. Before the change</d=
iv><div>loop was not breaking early, I fixed that as well in=C2=A0V2.</div>=
<div><br></div><div>Thanks,</div><div>Satya</div><div><br></div><div>=C2=A0=
</div></div></div>

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