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From: Amit Langote <[email protected]>
To: Tom Lane <[email protected]>
Cc: Etsuro Fujita <[email protected]>
Cc: Matheus Alcantara <[email protected]>
Cc: Ayush Tiwari <[email protected]>
Cc: Rafia Sabih <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Amit Langote <[email protected]>
Subject: Re: BUG #19484: Segmentation fault triggered by FDW
Date: Wed, 24 Jun 2026 12:50:28 +0900
Message-ID: <CA+HiwqFKFSSGg7Xygw6r3WK+HKOt6FXLTBuVOyFEH76_To9U8g@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On Wed, Jun 24, 2026 at 10:53 AM Tom Lane <[email protected]> wrote:
> Amit Langote <[email protected]> writes:
> > crake is now red on REL_18:
> > https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=crake&dt=2026-06-24%2000%3A02%3A03
>
> > It reports sizeof(ModifyTableState) grew by 8 bytes.
>
> > That’s from adding mt_fdwPrivLists at the end of the struct. Placing it
> > last keeps existing field offsets stable, which is what extensions reading
> > the node rely on, but it does grow the struct, which is what the checker
> > flags. I believe we’ve added trailing struct members in back branches
> > before for exactly this reason. Is a flagged sizeof increase acceptable
> > here under that precedent, or do we now want to avoid any flagged ABI
> > change on a back branch?
>
> I don't believe that the addition of ABI checking was meant to change
> our back-patching policies, just to make sure we don't make
> unintentional ABI changes.  As you say, we've added trailing fields
> before.  The critical question is whether it's likely that any
> extensions create their own ModifyTableState nodes (and might make
> them too small and/or fail to fill the new field correctly).
>
> I was about to say that that seems unlikely to me, but a check of
> Debian Code Search immediately found pg_rewrite doing it.  So yeah,
> looks like we'd better adopt the no-ABI-break solution.

Ah, ok, will post the patch to do so in the REL_18_STABLE branch.

Thanks for the comment.

-- 
Thanks, Amit Langote






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