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

On Fri, Nov 11, 2022 at 7:57 AM houzj(dot)fnst(at)fujitsu(dot)com
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> On Monday, November 7, 2022 6:18 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > Here are comments on v42-0001:
> >
> > We have the following three similar name functions regarding to
> > starting a new parallel apply worker:
> > ---
> > /*
> > * Exit if any parameter that affects the remote connection
> > was changed.
> > - * The launcher will start a new worker.
> > + * The launcher will start a new worker, but note that the
> > parallel apply
> > + * worker may or may not restart depending on the value of
> > the streaming
> > + * option and whether there will be a streaming transaction.
> >
> > In which case does the parallel apply worker don't restart even if the
> > streaming option has been changed?
>
> Sorry, I forgot to reply to this comment. If user change the streaming option from
> 'parallel' to 'on' or 'off', the parallel apply workers won't be restarted.
>

How about something like the below so as to be more explicit about
this in the comments?
diff --git a/src/backend/replication/logical/worker.c
b/src/backend/replication/logical/worker.c
index bfe326bf0c..74cd5565bd 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -3727,9 +3727,10 @@ maybe_reread_subscription(void)

/*
* Exit if any parameter that affects the remote connection was changed.
- * The launcher will start a new worker, but note that the
parallel apply
- * worker may or may not restart depending on the value of the streaming
- * option and whether there will be a streaming transaction.
+ * The launcher will start a new worker but note that the parallel apply
+ * worker won't restart if the streaming option's value is changed from
+ * 'parallel' to any other value or the server decides not to stream the
+ * in-progress transaction.
*/

--
With Regards,
Amit Kapila.