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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: Peter Smith <smithpb2250@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@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: 2023-01-17T02:21:04Z
Lists: pgsql-hackers 
On Tuesday, January 17, 2023 5:43 AM Peter Smith <smithpb2250@gmail.com> wrote:
> 
> On Mon, Jan 16, 2023 at 5:41 PM Amit Kapila <amit.kapila16@gmail.com>
> wrote:
> >
> > On Mon, Jan 16, 2023 at 10:24 AM Peter Smith <smithpb2250@gmail.com>
> wrote:
> > >
> > > 2.
> > >
> > >  /*
> > > + * Return the pid of the leader apply worker if the given pid is
> > > +the pid of a
> > > + * parallel apply worker, otherwise return InvalidPid.
> > > + */
> > > +pid_t
> > > +GetLeaderApplyWorkerPid(pid_t pid)
> > > +{
> > > + int leader_pid = InvalidPid;
> > > + int i;
> > > +
> > > + LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
> > > +
> > > + for (i = 0; i < max_logical_replication_workers; i++) {
> > > + LogicalRepWorker *w = &LogicalRepCtx->workers[i];
> > > +
> > > + if (isParallelApplyWorker(w) && w->proc && pid == w->proc->pid) {
> > > + leader_pid = w->leader_pid; break; } }
> > > +
> > > + LWLockRelease(LogicalRepWorkerLock);
> > > +
> > > + return leader_pid;
> > > +}
> > >
> > > 2a.
> > > IIUC the IsParallelApplyWorker macro does nothing except check that
> > > the leader_pid is not InvalidPid anyway, so AFAIK this algorithm
> > > does not benefit from using this macro because we will want to
> > > return InvalidPid anyway if the given pid matches.
> > >
> > > So the inner condition can just say:
> > >
> > > if (w->proc && w->proc->pid == pid)
> > > {
> > > leader_pid = w->leader_pid;
> > > break;
> > > }
> > >
> >
> > Yeah, this should also work but I feel the current one is explicit and
> > more clear.
> 
> OK.
> 
> But, I have one last comment about this function -- I saw there are already
> other functions that iterate max_logical_replication_workers like this looking
> for things:
> - logicalrep_worker_find
> - logicalrep_workers_find
> - logicalrep_worker_launch
> - logicalrep_sync_worker_count
> 
> So I felt this new function (currently called GetLeaderApplyWorkerPid) ought
> to be named similarly to those ones. e.g. call it something like
> "logicalrep_worker_find_pa_leader_pid".
> 

I am not sure we can use the name, because currently all the API name in launcher that
used by other module(not related to subscription) are like
AxxBxx style(see the functions in logicallauncher.h).
logicalrep_worker_xxx style functions are currently only declared in
worker_internal.h.

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.