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Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options - Mailing list pgsql-hackers

From	Krasiyan Andreev
Subject	Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options
Date	January 23 12:08:39
Msg-id	CAN1PwokSDfSkOmDk6sfdEOUz_mTm333-gkLOBPK=JrVsMJFZ1g@mail.gmail.com Whole thread Raw
In response to	Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options (Oliver Ford <ojford@gmail.com>)
List	pgsql-hackers

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Hi,

I was able to reproduce exactly the problem, with clean compile and --enable-cassert:

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 | 2
3 | | 2
(3 rows)

test=#

Also, make check errors out at window test (without --enable-cassert it was passed in previous compile):

krasiyan@fedora:~/pgsql-src/postgresql$ cat /home/krasiyan/pgsql-src/postgresql/src/test/regress/regression.diffs
diff -U3 /home/krasiyan/pgsql-src/postgresql/src/test/regress/expected/window.out /home/krasiyan/pgsql-src/postgresql/src/test/regress/results/window.out
--- /home/krasiyan/pgsql-src/postgresql/src/test/regress/expected/window.out 2025-01-22 21:25:47.114508215 +0200
+++ /home/krasiyan/pgsql-src/postgresql/src/test/regress/results/window.out 2025-01-23 07:58:26.784659592 +0200
@@ -5477,12 +5477,12 @@
name | orbit | lead | lead_respect | lead_ignore
---------+-------+-------+--------------+-------------
earth | | 4332 | 4332 | 4332
- jupiter | 4332 | | | 88
+ jupiter | 4332 | | |
mars | | 88 | 88 | 88
mercury | 88 | 60182 | 60182 | 60182
neptune | 60182 | 90560 | 90560 | 90560
pluto | 90560 | 24491 | 24491 | 24491
- saturn | 24491 | | | 224
+ saturn | 24491 | | |
uranus | | 224 | 224 | 224
venus | 224 | | |
xyzzy | | | |
@@ -5577,13 +5577,13 @@
name | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore
---------+-------+-------------+------------+-----------+-------------+------------
earth | | 4332 | 4332 | | 4332 |
- jupiter | 4332 | 88 | 88 | | 88 |
- mars | | 4332 | 60182 | 88 | 88 | 4332
- mercury | 88 | 4332 | 90560 | 60182 | 60182 | 4332
+ jupiter | 4332 | 88 | 88 | | 60182 |
+ mars | | 88 | 60182 | 60182 | 60182 | 4332
+ mercury | 88 | 4332 | 90560 | 90560 | 90560 | 4332
neptune | 60182 | 88 | 24491 | 90560 | 90560 | 88
- pluto | 90560 | 88 | 24491 | 60182 | 24491 | 60182
- saturn | 24491 | 60182 | 224 | 90560 | 224 | 90560
- uranus | | 90560 | 224 | 24491 | 224 | 24491
+ pluto | 90560 | 88 | 24491 | 60182 | 60182 | 60182
+ saturn | 24491 | 60182 | 224 | 90560 | 90560 | 90560
+ uranus | | 90560 | 224 | 24491 | 24491 | 24491
venus | 224 | 24491 | 24491 | | | 24491
xyzzy | | 224 | 224 | | | 224
(10 rows)
@@ -5646,14 +5646,14 @@
name | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore
---------+-------+-------------+------------+-----------+-------------+------------
earth | | | | | 88 |
- jupiter | | 88 | 88 | | 88 |
- mars | | 88 | 60182 | 60182 | 88 |
+ jupiter | | 88 | 88 | | 60182 |
+ mars | | 88 | 60182 | 60182 | 60182 |
mercury | 88 | 88 | 90560 | 60182 | 60182 |
- neptune | 60182 | 88 | 24491 | 60182 | 90560 | 88
- pluto | 90560 | 88 | 24491 | 60182 | 24491 | 60182
- saturn | 24491 | 60182 | 224 | 90560 | 224 | 90560
- uranus | | 90560 | 224 | 24491 | 224 | 24491
- venus | 224 | 24491 | 224 | 224 | | 24491
+ neptune | 60182 | 88 | 24491 | 60182 | 60182 | 88
+ pluto | 90560 | 88 | 24491 | 60182 | 60182 | 60182
+ saturn | 24491 | 60182 | 224 | 90560 | 90560 | 90560
+ uranus | | 90560 | 224 | 24491 | 24491 | 24491
+ venus | 224 | 24491 | 224 | 224 | 224 | 24491
xyzzy | | 224 | 224 | | | 224
(10 rows)

На чт, 23.01.2025 г. в 6:25 Tatsuo Ishii <ishii@postgresql.org> написа:

> 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

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Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options - Mailing list pgsql-hackers

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