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* BUG #18381: Invalid query generated by postgres_fdw with UNION ALL and ORDER BY
@ 2024-03-07 10:22 PG Bug reporting form <noreply@postgresql.org>
2024-03-07 11:32 ` Re: BUG #18381: Invalid query generated by postgres_fdw with UNION ALL and ORDER BY David Rowley <dgrowleyml@gmail.com>
0 siblings, 1 reply; 2+ messages in thread
From: PG Bug reporting form @ 2024-03-07 10:22 UTC (permalink / raw)
To: pgsql-bugs@lists.postgresql.org; +Cc: michal@kleczek.org
The following bug has been logged on the website:
Bug reference: 18381
Logged by: Michal Kleczek
Email address: michal@kleczek.org
PostgreSQL version: 16.2
Operating system: Linux
Description:
The following query:
SELECT * FROM (
SELECT 2023 AS year, * FROM remote_table_1
UNION ALL
SELECT 2022 AS year, * FROM remote_table_2
)
ORDER BY year DESC;
yields the following remote query:
SELECT [columns] FROM remote_table_1 ORDER BY 2023 DESC
and subsequently fails remote execution.
Not really sure where the problem is - the planner or postgres_fdw.
I guess it is postgres_fdw not filtering out ordering keys.
This filtering would also be pretty useful in the following scenario (which
is also why I went through UNION ALL route and discovered this issue):
I have a table partitioned by year, partitions are remote tables.
On remote servers I have a GIST index that does not support ordering ([1])
so I would like to avoid sending ORDER BY year to remote servers.
Ideally redundant ordering should be filtered out.
[1]
https://www.postgresql.org/message-id/B2AC13F9-6655-4E27-BFD3-068844E5DC91%40kleczek.org
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: BUG #18381: Invalid query generated by postgres_fdw with UNION ALL and ORDER BY
2024-03-07 10:22 BUG #18381: Invalid query generated by postgres_fdw with UNION ALL and ORDER BY PG Bug reporting form <noreply@postgresql.org>
@ 2024-03-07 11:32 ` David Rowley <dgrowleyml@gmail.com>
0 siblings, 0 replies; 2+ messages in thread
From: David Rowley @ 2024-03-07 11:32 UTC (permalink / raw)
To: michal@kleczek.org; pgsql-bugs@lists.postgresql.org
On Thu, 7 Mar 2024 at 23:35, PG Bug reporting form
<noreply@postgresql.org> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference: 18381
> Logged by: Michal Kleczek
> Email address: michal@kleczek.org
> PostgreSQL version: 16.2
> Operating system: Linux
> Description:
I see you've raised this on -hackers [1] already. Since there's
already some discussion and a proposed fix there, I think it's better
the discussion continues there.
David
[1] https://postgr.es/m/0714C8B8-8D82-4ABB-9F8D-A0C3657E7B6E@kleczek.org
^ permalink raw reply [nested|flat] 2+ messages in thread
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2024-03-07 10:22 BUG #18381: Invalid query generated by postgres_fdw with UNION ALL and ORDER BY PG Bug reporting form <noreply@postgresql.org>
2024-03-07 11:32 ` David Rowley <dgrowleyml@gmail.com>
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