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

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-12-17T14:04:14Z
Lists: pgsql-hackers

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On Saturday, December 17, 2022 8:16 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Fri, Dec 16, 2022 at 4:34 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Fri, Dec 16, 2022 at 2:47 PM houzj.fnst@fujitsu.com
> > <houzj.fnst@fujitsu.com> wrote:
> > >
> > > > ---
> > > > +       active_workers = list_copy(ParallelApplyWorkerPool);
> > > > +
> > > > +       foreach(lc, active_workers)
> > > > +       {
> > > > +               int                     slot_no;
> > > > +               uint16          generation;
> > > > +               ParallelApplyWorkerInfo *winfo =
> > > > (ParallelApplyWorkerInfo *) lfirst(lc);
> > > > +
> > > > +               LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
> > > > +               napplyworkers =
> > > > logicalrep_pa_worker_count(MyLogicalRepWorker->subid);
> > > > +               LWLockRelease(LogicalRepWorkerLock);
> > > > +
> > > > +               if (napplyworkers <=
> > > > max_parallel_apply_workers_per_subscription / 2)
> > > > +                       return;
> > > > +
> > > >
> > > > Calling logicalrep_pa_worker_count() with lwlock for each worker
> > > > seems not efficient to me. I think we can get the number of
> > > > workers once at the top of this function and return if it's
> > > > already lower than the maximum pool size. Otherwise, we attempt to stop
> extra workers.
> > >
> > > How about we directly check the length of worker pool list here
> > > which seems simpler and don't need to lock ?
> > >
> >
> > I don't see any problem with that. Also, if such a check is safe then
> > can't we use the same in pa_free_worker() as well? BTW, shouldn't
> > pa_stop_idle_workers() try to free/stop workers unless the active
> > number reaches below max_parallel_apply_workers_per_subscription?
> >
> 
> BTW, can we move pa_stop_idle_workers() functionality to a later patch (say into
> v61-0006*)? That way we can focus on it separately once the main patch is
> committed.

Agreed. I have addressed all the comments and did some cosmetic changes.
Attach the new version patch set.

Best regards,
Hou zj

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.