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From: Pavan Deolasee <pavan.deolasee@gmail.com>
Date: Fri, 15 Nov 2024 23:39:24 +0530
Message-ID: <CABOikdMOAu6666_xWCPOfCxg4NzHE9tU-WVSpw3rbzUmDyW9fA@mail.gmail.com>
Subject: Re: Potential ABI breakage in upcoming minor releases
To: Noah Misch <noah@leadboat.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Aleksander Alekseev <aleksander@timescale.com>, 
	pgsql-hackers <pgsql-hackers@postgresql.org>, Marco Slot <marco.slot@gmail.com>, 
	Alvaro Herrera <alvherre@alvh.no-ip.org>, Christoph Berg <myon@debian.org>
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On Fri, Nov 15, 2024 at 11:22=E2=80=AFPM Noah Misch <noah@leadboat.com> wro=
te:

>
>
> > I'm starting to lean to the opinion that we need a re-wrap.
>
> Perhaps.  Even if we do rewrap for some reason, it's not a given that
> restoring the old struct size is net beneficial.  If we restore the old
> struct
> size in v16.6, those who rebuild for v16.5 would need to rebuild again.
> Hearing about other ResultRelInfo arrays will help clarify that decision.
>

Looking more carefully at the usage of `ResultRelInfo` in the PGD code, I
think we might also be impacted by it. At one place, we loop through the
`es_result_relations` array and a size mismatch there will cause problems.
Interestingly, in v14 and above, we read from `es_opened_result_relations`,
which is a List, so it should be safe. I will try some tests on v13 to see
if they result in crashes. But it seems quite likely by reading the code.

Thanks,
Pavan

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><div class=3D"gmail_quote"><div=
 dir=3D"ltr" class=3D"gmail_attr">On Fri, Nov 15, 2024 at 11:22=E2=80=AFPM =
Noah Misch &lt;<a href=3D"mailto:noah@leadboat.com">noah@leadboat.com</a>&g=
t; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0p=
x 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color=
:rgb(204,204,204);padding-left:1ex"><br>
<br>
&gt; I&#39;m starting to lean to the opinion that we need a re-wrap.<br>
<br>
Perhaps.=C2=A0 Even if we do rewrap for some reason, it&#39;s not a given t=
hat<br>
restoring the old struct size is net beneficial.=C2=A0 If we restore the ol=
d struct<br>
size in v16.6, those who rebuild for v16.5 would need to rebuild again.<br>
Hearing about other ResultRelInfo arrays will help clarify that decision.<b=
r></blockquote><div><br></div><div>Looking more carefully at the usage of `=
ResultRelInfo` in the PGD code, I think we might also be impacted by it. At=
 one place, we loop through the `es_result_relations` array and a size mism=
atch there will cause problems. Interestingly, in v14 and above, we read fr=
om `es_opened_result_relations`, which is a List, so it should be safe. I w=
ill try some tests on v13 to see if they result in crashes. But it seems qu=
ite likely by reading the code.</div><div><br></div><div>Thanks,</div><div>=
Pavan</div><div><br></div><div>=C2=A0</div></div></div>

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