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Re: Improving the latch handling between logical replication launcher and worker processes. - Mailing list pgsql-hackers

From vignesh C
Subject Re: Improving the latch handling between logical replication launcher and worker processes.
Date
Msg-id CALDaNm19H0qTWEp0B8ovqwSo7BtyCG0wpw__4OW4c2aJ+jK6TQ@mail.gmail.com
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In response to RE: Improving the latch handling between logical replication launcher and worker processes.  ("Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>)
Responses Re: Improving the latch handling between logical replication launcher and worker processes.
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On Fri, 10 May 2024 at 07:39, Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
>
> Dear Vignesh,
>
> Thanks for raising idea!
>
> > a) Introduce a new latch to handle worker attach and exit.
>
> Just to confirm - there are three wait events for launchers, so I feel we may be
> able to create latches per wait event. Is there a reason to introduce
> "a" latch?

One latch is enough, we can use the new latch for both worker starting
and worker exiting. The other existing latch can be used for other
purposes.  Something like the attached patch.

Regards,
Vignesh
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From: Andrei Lepikhov
Date:
Subject: About 0001:,Having overviewed it, I don't see any issues (but I'm the author), except grammatical ones - but I'm not a native to judge it.,Also, the sentence 'turning GROUP BY clauses into pathkeys' is unclear to me. It may be better to write something like: 'building pathkeys by the list of grouping clauses'.,,0002:,The part under USE_ASSERT_CHECKING looks good to me. But the code in group_keys_reorder_by_pathkeys looks suspicious: of course, we do some doubtful work without any possible way to reproduce, but if we envision some duplicated elements in the group_clauses, we should avoid usage of the list_concat_unique_ptr. What's more, why do you not exit from foreach_ptr immediately after SortGroupClause has been found? I think the new_group_clauses should be consistent with the new_group_pathkeys.,,0003:,Looks good,,0004:,I was also thinking about reintroducing the preprocess_groupclause because with the re-arrangement of GROUP-BY clauses according to incoming pathkeys, it doesn't make sense to have a user-defined order—at least while cost_sort doesn't differ costs for alternative column orderings.,So, I'm okay with the code. But why don't you use the same approach with foreach_ptr as before?
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From: vignesh C
Date:
Subject: Re: Improving the latch handling between logical replication launcher and worker processes.