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

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>
Cc: "kuroda.hayato@fujitsu.com" <kuroda.hayato@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Peter Smith <smithpb2250@gmail.com>
Date: 2022-08-11T06:43:16Z
Lists: pgsql-hackers 
On Thu, Aug 4, 2022 at 12:07 PM wangw.fnst@fujitsu.com
<wangw.fnst@fujitsu.com> wrote:
>
> On Thurs, Jul 28, 2022 at 13:20 PM Kuroda, Hayato/黒田 隼人 <kuroda.hayato@fujitsu.com> wrote:
> >
> > Dear Wang-san,
> >
> > Hi, I'm also interested in the patch and I started to review this.
> > Followings are comments about 0001.
>
> Thanks for your kindly review and comments.
> To avoid making this thread too long, I will reply to all of your comments
> (#1~#13) in this email.
>
> > 1. terminology
> >
> > In your patch a new worker "apply background worker" has been introduced,
> > but I thought it might be confused because PostgreSQL has already the worker
> > "background worker".
> > Both of apply worker and apply bworker are categolized as bgworker.
> > Do you have any reasons not to use "apply parallel worker" or "apply streaming
> > worker"?
> > (Note that I'm not native English speaker)
>
> Since we will later consider applying non-streamed transactions in parallel, I
> think "apply streaming worker" might not be very suitable. I think PostgreSQL
> also has the worker "parallel worker", so for "apply parallel worker" and
> "apply background worker", I feel that "apply background worker" will make the
> relationship between workers more clear. ("[main] apply worker" and "apply
> background worker")
>

But, on similar lines, we do have vacuumparallel.c for parallelizing
index vacuum. I agree with Kuroda-San on this point that the currently
proposed terminology doesn't sound to be very clear. The other options
that come to my mind are "apply streaming transaction worker", "apply
parallel worker" and file name could be applystreamworker.c,
applyparallel.c, applyparallelworker.c, etc. I see the point why you
are hesitant in calling it "apply parallel worker" but it is quite
possible that even for non-streamed xacts, we will share quite some
part of this code.

Thoughts?

-- 
With Regards,
Amit Kapila.

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.