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

On Sunday, January 8, 2023 10:14 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Sat, Jan 7, 2023 at 2:25 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
>
> Today, I was analyzing this patch w.r.t recent commit c6e1f62e2c and found that
> pa_set_xact_state() should set the latch (wake up) for the leader worker as the
> leader could be waiting in pa_wait_for_xact_state(). What do you think? But
> otherwise, it should be okay w.r.t DDLs because this patch allows the leader
> worker to restart logical replication for subscription parameter change which will
> in turn stop/restart parallel workers if required.

Thanks for the analysis. I agree that it would be better to signal the leader
when setting the state to PARALLEL_TRANS_STARTED, otherwise it might slightly
delay the timing of catch the state change in pa_wait_for_xact_state(), so I
have updated the patch for the same. Besides, I also checked commit c6e1f62e2c,
I think DDL operation doesn't need to wake up the parallel apply worker
directly as the parallel apply worker doesn't start table sync and only
communicate with the leader, so I didn't find some other places that need to be
changed.

Attach the updated patch set.

Best regards,
Hou zj