Re: Single transaction in the tablesync worker?

On Wed, Jan 13, 2021 at 1:07 PM Hou, Zhijie <houzj(dot)fnst(at)cn(dot)fujitsu(dot)com> wrote:
>
> > Also PSA some detailed logging evidence of some test scenarios involving
> > Drop/AlterSubscription:
> > + Test-20210112-AlterSubscriptionRefresh-ok.txt =
> > AlterSubscription_refresh which successfully drops a tablesync slot
> > + Test-20210112-AlterSubscriptionRefresh-warning.txt =
> > AlterSubscription_refresh gives WARNING that it cannot drop the tablesync
> > slot (which no longer exists)
> > + Test-20210112-DropSubscription-warning.txt = DropSubscription with a
> > disassociated slot_name gives a WARNING that it cannot drop the tablesync
> > slot (due to broken connection)
>
> Hi
>
> > * The AlterSubscription_refresh (v14+) is now more similar to DropSubscription w.r.t to stopping workers for any "removed" tables.
> I have an issue about the above feature.
>
> With the patch, it seems does not stop the worker in the case of [1].
> I probably missed something, should we stop the worker in such case ?
>
> [1] https://www.postgresql.org/message-id/CALj2ACV%2B0UFpcZs5czYgBpujM9p0Hg1qdOZai_43OU7bqHU_xw%40mail.gmail.com
>

I am not exactly sure of the concern. (If the extra info below does
not help can you please describe your concern with more details).

This [v14] patch code/feature is only referring to the immediate
stopping of only the *** "tablesync" *** worker (if any) for any/each
table being removed from the subscription. It has nothing to say about
the "apply" worker of the subscription, which continues replicating as
before.

OTOH, I think the other mail problem is not really related to the
"tablesync" workers. As you can see (e.g. steps 7,8,9,10 of [2]), that
problem is described as continuing over multiple transactions to
replicate unexpected rows - I think this could only be done by the
subscription "apply" worker, and is after the "tablesync" worker has
gone away.

So AFAIK these are 2 quite unrelated problems, and would be solved
independently.

It just happens that they are both exposed using ALTER SUBSCRIPTION
... REFRESH PUBLICATION;

----
[v14] = https://www.postgresql.org/message-id/CAHut%2BPsPO2vOp%2BP7U2szROMy15PKKGanhUrCYQ0ffpy9zG1V1A%40mail.gmail.com
[2] = https://www.postgresql.org/message-id/CALj2ACV%2B0UFpcZs5czYgBpujM9p0Hg1qdOZai_43OU7bqHU_xw%40mail.gmail.com

Kind Regards,
Peter Smith.
Fujitsu Australia