Re: Single transaction in the tablesync worker?

On Thu, Feb 4, 2021 at 9:55 AM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
>
> On Wed, Feb 3, 2021 at 11:38 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> > Thanks for the report. The problem here was that the error occurred
> > when we were trying to copy the large data. Now, before fetching the
> > entire data we issued a rollback that led to this problem. I think the
> > alternative here could be to first fetch the entire data when the
> > error occurred then issue the following commands. Instead, I have
> > modified the patch to perform 'drop_replication_slot' in the beginning
> > if the relstate is datasync. Do let me know if you can think of a
> > better way to fix this?
>
> I have verified that the problem is not seen after this patch. I also
> agree with the approach taken for the fix,
>

Thanks. I have fixed one of the issues reported by me earlier [1]
wherein the tablesync worker can repeatedly fail if after dropping the
slot there is an error while updating the SYNCDONE state in the
database. I have moved the drop of the slot just before commit of the
transaction where we are marking the state as SYNCDONE. Additionally,
I have removed unnecessary includes in tablesync.c, updated the docs
for Alter Subscription, and updated the comments at various places in
the patch. I have also updated the commit message this time.

I am still not very happy with the way we handle concurrent drop
origins but probably that would be addressed by the other patch Peter
is working on [2].

[1] - https://www.postgresql.org/message-id/CAA4eK1JdWv84nMyCpTboBURjj70y3BfO1xdy8SYPRqNxtH7TEA%40mail.gmail.com
[2] - https://www.postgresql.org/message-id/CAHut%2BPsW6%2B7Ucb1sxjSNBaSYPGAVzQFbAEg4y1KsYQiGCnyGeQ%40mail.gmail.com

--
With Regards,
Amit Kapila.