Horton

Re: BUG #18280: logical decoding build wrong snapshot for subtransactions

feichanghong <feichanghong@qq.com>

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From: feichanghong <feichanghong@qq.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-bugs <pgsql-bugs@lists.postgresql.org>
Date: 2024-01-24T11:01:44Z
Lists: pgsql-bugs

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  1. Fix catalog lookup due to wrong snapshot for subtransactions during decoding.

  2. Fix catalog lookup with the wrong snapshot during logical decoding.

Thank you for your correction.

> On Jan 24, 2024, at 17:18, Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> While looking closely at the test result, I wondered how the following
> part of test "s0_begin" "s0_truncate" "s1_checkpoint" "s1_get_changes"
> "s0_insert_part" "s1_get_changes" "s0_commit" can see the insert when
> the containing transaction is not yet committed. Then, I found it is
> because the insert is performed from session 1 due to way it is
> declared.
> 
> session "s1"
> ...
> step "s1_get_changes" { SELECT data FROM
> pg_logical_slot_get_changes('isolation_slot', NULL, NULL,
> 'skip-empty-xacts', '1', 'include-xids', '0'); }
> +step "s0_insert_part" { INSERT INTO tbl1_part VALUES (1); }
> 
> I think this session should be performed from seesion-1 and we need
> one more get_changes() call to see the problem. I have modified the
> test accordingly and also changed the comments. See the attached and
> let me know what you people think.

I'm very sorry for confusing you due to my mistake. In my original patch,
"s0_insert_part" should be "s1_insert_part" in session "s1", and after
confirmation, the problem can be reproduced.
Of course your fix is totally correct for me.


Best Regards,
Fei Changhong
Alibaba Cloud Computing Ltd.