Horton
Menu

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

Masahiko Sawada <sawada.mshk@gmail.com>

View thread
From: Masahiko Sawada <sawada.mshk@gmail.com>
To: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
Cc: Peter Smith <smithpb2250@gmail.com>, shveta malik <shveta.malik@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>
Date: 2023-01-17T14:37:02Z
Lists: pgsql-hackers 
On Tue, Jan 17, 2023 at 6:14 PM houzj.fnst@fujitsu.com
<houzj.fnst@fujitsu.com> wrote:
>
> On Tuesday, January 17, 2023 2:46 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Tue, Jan 17, 2023 at 12:37 PM houzj.fnst@fujitsu.com
> > <houzj.fnst@fujitsu.com> wrote:
> > > Attach the new version 0001 patch which addressed all other comments.
> > >
> >
> > Thank you for updating the patch. Here is one comment:
> >
> > @@ -426,14 +427,24 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
> >
> >                                 /*
> >                                  * Show the leader only for active parallel
> > workers.  This
> > -                                * leaves the field as NULL for the
> > leader of a parallel
> > -                                * group.
> > +                                * leaves the field as NULL for the
> > leader of a parallel group
> > +                                * or the leader of parallel apply workers.
> >                                  */
> >                                 if (leader && leader->pid !=
> > beentry->st_procpid)
> >                                 {
> >                                         values[28] =
> > Int32GetDatum(leader->pid);
> >                                         nulls[28] = false;
> >                                 }
> > +                               else
> > +                               {
> > +                                       int
> > leader_pid = GetLeaderApplyWorkerPid(beentry->st_procpid);
> > +
> > +                                       if (leader_pid != InvalidPid)
> > +                                       {
> > +                                               values[28] =
> > Int32GetDatum(leader_pid);
> > +                                               nulls[28] = false;
> > +                                       }
> > +                               }
> >                         }
> >
> > I'm slightly concerned that there could be overhead of executing
> > GetLeaderApplyWorkerPid () for every backend process except for parallel
> > query workers. The number of such backends could be large and
> > GetLeaderApplyWorkerPid() acquires the lwlock. For example, does it make
> > sense to check (st_backendType == B_BG_WORKER) before calling
> > GetLeaderApplyWorkerPid()? Or it might not be a problem since it's
> > LogicalRepWorkerLock which is not likely to be contended.
>
> Thanks for the comment and I think your suggestion makes sense.
> I have added the check before getting the leader pid. Here is the new version patch.

Thank you for updating the patch. Looks good to me.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.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.