Re: Fix duplicate detection for null-treatment window functions

> On Jul 18, 2026, at 10:19, Tatsuo Ishii <ishii(at)postgresql(dot)org> wrote:
>
>>>>> Happy to send a patch along these lines if you agree.
>>>>>
>>>>
>>>> I think your analysis is correct, please feel free to post your version.
>>>
>>> Thanks, Chao. Patch attached.
>>>
>>> It drops the redundant "&& wfunc->ignore_nulls == perfunc[i].ignore_nulls"
>>> term together with WindowStatePerFuncData.ignore_nulls, and rewords the
>>> now-stale comment, leaving equal() to distinguish calls that differ only
>>> in null treatment -- which it already does, since WindowFunc.ignore_nulls
>>> is a plain scalar field that _equalWindowFunc() compares. This fixes the
>>> same bug your v2 fixed, but removes the hand-maintained shadow copy that
>>> was the root cause, so it can't silently drift out of sync again.
>
> Yeah, in nodeWindowAgg.c, actually ignore_nulls checking is performed
> using WindowObject.ignore_nulls. I agree with your analysis.
>
>>> Testing:
>>> - Since the patch changes the layout of WindowStatePerFuncData, I also
>>> built the whole tree with -fsanitize=alignment,undefined
>>> -fno-sanitize-recover=alignment and re-ran make check under it: 245/245,
>>> no runtime errors. The removed byte sat right before an 8-byte-aligned
>>> pointer (winobj), so it was absorbed by padding and no following field
>>> offset changes.
>
> Thanks for the checking.
>
>> V2 overall looks good. One comment: I don’t think we need to add a comment explaining the equal() behavior for ignore_nulls.
>>
>> The duplicate detection logic is legacy. Commit 25a30bbd4 intended to handle ignore_nulls specially, so it added “which needs the same ignore_nulls value” to the comment. Since equal() already handles ignore_nulls natively, the code change that added special handling for ignore_nulls has been reverted, so I think the comment should just be reverted as well.
>
> Fair enough.
>
>> PFA v3, reverted the comment.
>
> Looks good to me except the comment line needs indentation fixing. v4
> patch attached. If there's no objection, I will commit it.
>
> Regards,
> --
> Tatsuo Ishii
> SRA OSS K.K.
> English: http://www.sraoss.co.jp/index_en/
> Japanese:http://www.sraoss.co.jp
> <v4-0001-Remove-redundant-null-treatment-check-in-window-f.patch>

V4 looks good to me.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/