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From: Lukas Fittl <lukas@fittl.com>
Date: Wed, 28 Jan 2026 21:44:26 -0800
Message-ID: <CAP53PkwZ1ZTMARKg6iEfAw9qzBhkjBitj-9gr_Jvy7k2AwGgWA@mail.gmail.com>
Subject: Re: pg_plan_advice
To: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>
Cc: Jacob Champion <jacob.champion@enterprisedb.com>, Dian Fay <di@nmfay.com>, 
	Matheus Alcantara <matheusssilv97@gmail.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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> Robert Haas <robertmhaas@gmail.com> writes:
> > That rearrangement got done in v11, and I've now committed that patch
> > after fixing a few typos that I found. Cautiously, woohoo, but let's
> > see if anything breaks.

Yay!

On Wed, Jan 28, 2026 at 6:41=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> skink's not happy:
>
> =3D2162940=3D=3D VALGRINDERROR-BEGIN
> =3D=3D2162940=3D=3D Conditional jump or move depends on uninitialised val=
ue(s)
> =3D=3D2162940=3D=3D    at 0x434D366: cost_material (costsize.c:2593)
> =3D=3D2162940=3D=3D    by 0x436E7E9: materialize_finished_plan (createpla=
n.c:6531)
> =3D=3D2162940=3D=3D    by 0x4383054: standard_planner (planner.c:533)
> ...
> =3D=3D2162940=3D=3D    by 0x44CD09D: ProcessUtility (utility.c:525)
> =3D=3D2162940=3D=3D  Uninitialised value was created by a stack allocatio=
n
> =3D=3D2162940=3D=3D    at 0x436E76A: materialize_finished_plan (createpla=
n.c:6506)
>

From a quick look, I think that's a missing initialization of
path->parallel_workers when cost_material gets called with the dummy
path created in materialize_finished_plan.

The indirect relationship between those functions doesn't seem great
(i.e. anything that gets read in cost_material has to be initialized
in materialize_finished_plan). What if we just zero initialize the
dummy Path structure instead, like in the attached?

Thanks,
Lukas

--
Lukas Fittl

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