Re: Skipping logical replication transactions on subscriber side

On Thu, Dec 9, 2021 at 2:24 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Thu, Dec 9, 2021 at 11:47 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > I am thinking that we can start a transaction, update the catalog,
> > commit that transaction. Then start a new one to update
> > origin_lsn/timestamp, finishprepared, and commit it. Now, if it
> > crashes after the first transaction, only commit prepared will be
> > resent again and this time we don't need to update the catalog as that
> > entry would be already cleared.
>
> Sounds good. In the crash case, it should be fine since we will just
> commit an empty transaction. The same is true for the case where
> skip_xid has been changed after skipping and preparing the transaction
> and before handling commit_prepared.
>
> Regarding the case where the user specifies XID of the transaction
> after it is prepared on the subscriber (i.g., the transaction is not
> empty), we won’t skip committing the prepared transaction. But I think
> that we don't need to support skipping already-prepared transaction
> since such transaction doesn't conflict with anything regardless of
> having changed or not.
>

Yeah, this makes sense to me.

--
With Regards,
Amit Kapila.