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

On Tuesday, January 17, 2023 11:32 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> On Tue, Jan 17, 2023 at 1:21 PM houzj(dot)fnst(at)fujitsu(dot)com
> <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> >
> > On Tuesday, January 17, 2023 5:43 AM Peter Smith
> <smithpb2250(at)gmail(dot)com> wrote:
> > >
> > > On Mon, Jan 16, 2023 at 5:41 PM Amit Kapila
> > > <amit(dot)kapila16(at)gmail(dot)com>
> > > wrote:
> > > >
> > > > On Mon, Jan 16, 2023 at 10:24 AM Peter Smith
> > > > <smithpb2250(at)gmail(dot)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.
> >
>
> OK. I didn't know there was another header convention that you were following.
> In that case, it is fine to leave the name as-is.

Thanks for confirming!

Attach the new version 0001 patch which addressed all other comments.

Best regards,
Hou zj