Date: Thu, 23 Jan 2025 13:25:02 +0900 (JST)
Message-Id: <20250123.132502.1946260197628893279.ishii@postgresql.org>
To: krasiyan@gmail.com
Cc: ojford@gmail.com, tgl@sss.pgh.pa.us, vik@postgresfriends.org,
 pgsql-hackers@postgresql.org, andrew@tao11.riddles.org.uk, david@fetter.org
Subject: Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options
From: Tatsuo Ishii <ishii@postgresql.org>
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	<20250122.205818.930169577391749915.ishii@postgresql.org>
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> Hello,
> I also played with the v4 patch and it produces correct result:
> test=# SELECT x,y,lead(y) IGNORE NULLS OVER (ORDER BY x) FROM
> (VALUES(1,NULL),(2,2),(3,NULL)) AS v(x,y);
>  x | y | lead
> ---+---+------
>  1 |   |    2
>  2 | 2 |
>  3 |   |
> (3 rows)
> 
> test=#
> It is from today's git, clean compile and install with only v4 patch
> applied, make check also passes without errors.

I guess you are just lucky. In my case I enabled --enable-cassert to
build PostgreSQL and it automatically turn on CLOBBER_FREED_MEMORY and
freed memory area is scrambled. If I look the patch closer, I found a
problem:

+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
:
:
+		winobj->win_nonnulls = palloc_array(int64, 16);

WinCheckAndInitializeNullTreatment is called in each built-in window
function. Window functions are called in the per tuple memory context,
which means win_nonnulls disappears when next tuple is supplied to the
window function. If my understanding is correct, winobj->win_nonnulls
needs to survive across processing tuples.

Best reagards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp