Re: BUG #19405: Assertion in eval_windowaggregates() fails due to integer overflow

On Tue, Feb 17, 2026 at 10:55 AM Richard Guo <guofenglinux(at)gmail(dot)com> wrote:
> I've included test cases covering the overflow scenarios for ROWS mode
> in v3. (I failed to come up with queries for GROUPS mode that
> demonstrate the bug, but I suspect I just haven't found the right test
> case yet.) I have also included a commit message.

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.

- Richard