Re: BUG #18526: 'UPDATE' inconsistency using index scan with 'NOT EXIST' after upgrading to PostgreSQL 16

Feliphe Pozzer <feliphepozzer@gmail.com>

From: Feliphe Pozzer <feliphepozzer@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-bugs@lists.postgresql.org, Richard Guo <guofenglinux@gmail.com>
Date: 2024-06-28T20:32:38Z
Lists: pgsql-bugs
Hello Tom, I applied the patch you suggested, and it appears that the issue
has been resolved.

Em sex., 28 de jun. de 2024 às 16:45, Feliphe Pozzer <
feliphepozzer@gmail.com> escreveu:

>   I am currently in the process of familiarizing myself with the steps
> required to compile and run the PostgreSQL code. As this will take some
> time, I wanted to let you know that I will begin testing the patch as soon
> as I am ready.  Thank you for your understanding and patience.
>
> Em sex., 28 de jun. de 2024 às 16:13, Tom Lane <tgl@sss.pgh.pa.us>
> escreveu:
>
>> PG Bug reporting form <noreply@postgresql.org> writes:
>> > Expected Result: All records that meet the criteria should be updated
>> > regardless of using index scan or seq scan.
>> > Actual Result: When PostgreSQL 16 uses index scan, it fails to find and
>> > update all records. By changing random_page_cost to a value that forces
>> the
>> > use of seq scan, all records are updated correctly.
>>
>> I see that the problematic plan involves a Merge Right Anti Join step,
>> which makes me guess that this is the same bug recently reported in
>>
>>
>> https://www.postgresql.org/message-id/flat/18522-c7a8956126afdfd0%40postgresql.org
>>
>> Are you in a position to try the patch posted in that thread?
>>
>>                         regards, tom lane
>>
>