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Re: Perform streaming logical transactions by background workers and parallel apply

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-01-06T07:31:02Z
Lists: pgsql-hackers 
On Fri, Jan 6, 2023 at 12:59 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> > > 3.
> > > +        else if (shmq_res == SHM_MQ_WOULD_BLOCK)
> > > +        {
> > > +            /* Replay the changes from the file, if any. */
> > > +            if (pa_has_spooled_message_pending())
> > > +            {
> > > +                pa_spooled_messages();
> > > +            }
> > >
> > > I think we do not need this pa_has_spooled_message_pending() function.
> > > Because this function is just calling pa_get_fileset_state() which is
> > > acquiring mutex and getting filestate then if the filestate is not
> > > FS_EMPTY then we call pa_spooled_messages() that will again call
> > > pa_get_fileset_state() which will again acquire mutex.  I think when
> > > the state is FS_SERIALIZE_IN_PROGRESS it will frequently call
> > > pa_get_fileset_state() consecutively 2 times, and I think we can
> > > easily achieve the same behavior with just one call.
> > >
> >
> > This is just to keep the code easy to follow. As this would be a rare
> > case, so thought of giving preference to code clarity.
>
> I think the code will be simpler with just one function no? I mean
> instead of calling pa_has_spooled_message_pending() in if condition
> what if we directly call pa_spooled_messages();, this is anyway
> fetching the file_state and if the filestate is EMPTY then it can
> return false, and if it returns false we can execute the code which is
> there in else condition.  We might need to change the name of the
> function though.
>
But anyway it is not a performance-critical path so if you think the
current way looks cleaner then I am fine with that too.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix invalid memory access during the shutdown of the parallel apply worker.

  2. Fix assertion failure in apply worker.

  3. Use elog to report unexpected action in handle_streamed_transaction().

  4. Use appropriate wait event when sending data in the apply worker.

  5. Allow the logical_replication_mode to be used on the subscriber.

  6. Rename GUC logical_decoding_mode to logical_replication_mode.

  7. Display the leader apply worker's PID for parallel apply workers.

  8. Improve the code to decide and process the apply action.

  9. Document the newly added wait events added by commit 216a784829.

  10. Perform apply of large transactions by parallel workers.

  11. Wake up a subscription's replication worker processes after DDL.

  12. Add copyright notices to meson files

  13. Better document logical replication parameters

  14. Add a common function to generate the origin name.

  15. Harmonize parameter names in storage and AM code.

  16. Avoid using list_length() to test for empty list.

  17. Improve two comments related to a boolean DefElem's value

  18. Fix partition table's REPLICA IDENTITY checking on the subscriber.

  19. Fix data inconsistency between publisher and subscriber.

  20. Fix cache look-up failures while applying changes in logical replication.