Horton

Re: Should IGNORE NULLS cache nullness for volatile arguments?

Chao Li <li.evan.chao@gmail.com>

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From: Chao Li <li.evan.chao@gmail.com>
To: Tatsuo Ishii <ishii@postgresql.org>
Cc: pgsql-hackers@postgresql.org, ojford@gmail.com
Date: 2026-05-15T03:08:54Z
Lists: pgsql-hackers

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  1. Fix IGNORE NULLS nullness cache for volatile window arguments.

Attachments


> On May 14, 2026, at 20:56, Tatsuo Ishii <ishii@postgresql.org> wrote:
> 
> Hi Chao,
> 
>>> The attached patch makes a small change in that direction. It only uses the IGNORE NULLS nullness cache when the argument is safe to reuse. For non-cacheable arguments, the nullness is treated as unknown and the argument is evaluated again.
>>> 
>>> See the attached patch for details.
>> 
>> I will look into the patches.
> 
> @@ -3454,7 +3455,10 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
> if (isout)
> *isout = false;
> 
> - v = get_notnull_info(winobj, abs_pos, argno);
> + if (winobj->notnull_info_cacheable[argno])
> 
> What about moving this if statement inside get_notnull_info() so that
> the caller does not care about this argno is cacheable or not?
> 
> + /* record the row status if it is safe to reuse */
> + if (winobj->notnull_info_cacheable[argno])
> + put_notnull_info(winobj, abs_pos, argno, *isnull);
> 
> Similary, we can move "if (winobj->notnull_info_cacheable[argno])" inside put_notnull_info().
> 

Yep, good idea. Addressed in attached v2.

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