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From: Richard Guo <guofenglinux@gmail.com>
Date: Fri, 10 Apr 2026 18:24:14 +0900
Message-ID: <CAMbWs4-1J+WQFVR9=+gCgqugxoS=ecjiQ2t5GfLGDUgG7X2uqA@mail.gmail.com>
Subject: Re: BUG #19405: Assertion in eval_windowaggregates() fails due to
 integer overflow
To: Tender Wang <tndrwang@gmail.com>
Cc: exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
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On Wed, Apr 8, 2026 at 6:42=E2=80=AFPM Richard Guo <guofenglinux@gmail.com>=
 wrote:
> Here is the updated patch.  I've added test cases for GROUPS mode with
> an overflow-inducing offset.  These don't seem to produce visibly
> wrong results without the patch.  I believe that is because the
> incremental nature of group pointer advancement happens to mask the
> misbehavior.  But I think they are still worth having since signed
> integer overflow is undefined behavior in C.
>
> Regarding performance, I don't think this should be a concern.
> pg_add_s64_overflow compiles down to a native add+jo sequence on
> platforms with __builtin_add_overflow, and falls back to a couple of
> inlined comparisons on others.  Either way, the cost seems negligible
> next to the per-row tuple store and aggregation work these functions
> already do.

I forgot to mention that I've committed and back-patched this fix.

- Richard