Alexander Korotkov писал(а) 2025-03-18 14:19:
Hi, Alexander!
On Tue, Mar 18, 2025 at 1:13 PM Alexander Pyhalov
<a.pyha...@postgrespro.ru> wrote:
Alexander Korotkov писал(а) 2025-03-18 03:27:
> Hi, Robins!
>
> On Tue, Mar 18, 2025 at 2:20 AM Robins Tharakan <thara...@gmail.com>
> wrote:
>> On Mon, 4 Dec 2023 at 07:22, Alexander Korotkov <aekorot...@gmail.com>
>> wrote:
>> >
>> >
>> > Now, I think this looks good. I'm going to push this if no objections.
>>
>> After this commit, I began seeing an unexpected ERROR - see this
>> bug-report.
>> https://www.postgresql.org/message-id/18852-fb75b88160678f78%40postgresql.org
>
> Thank you for pointing.
> I'll check this in the next couple of days.
>
It seems conditions, coming from semi-joins, are handled incorrectly
under left and right join. When deparsing left/right joins and there
are
semi-joins in inner or outer part of the query, the corresponding part
is deparsed as subquery. And we can't refer subquery vars from above,
so
just should not pull up the restrictinfos. The attached patch does
exactly this.
Thank you for the fix. It looks like this fix generally affects
left/right joins, not just semi-joins. Can you confirm this doesn't
cause regression for other cases?
Hi.
This shouldn't. When semi-join is found below left/right join, it's
deparsed as subquery.
Interesting enough, this mechanics (deparsing as subquery) is used
1) for semi-joins under left/right join,
2) for full outer joins when inner or outer part has some remote_conds.
The issue here is that after subquery is deparsed, we don't consider if
its target attributes are available to the upper level
join . As for semi-join itself, all conditions are still deparsed on
left/right join boundary, they are just not propagated further.
This shouldn't be a problem, as they are evaluated in subquery. As for
left/right join without semi-join beneath it - its behavior is not
affected
(as hidden_subquery_rels is empty).
--
Best regards,
Alexander Pyhalov,
Postgres Professional
