On Tue, Mar 1, 2022 at 8:31 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> I’ve considered a plan for the skipping logical replication
> transaction feature toward PG15. Several ideas and patches have been
> proposed here and another related thread[1][2] for the skipping
> logical replication transaction feature as follows:
>
> A. Change pg_stat_subscription_workers (committed 7a8507329085)
> B. Add origin name and commit-LSN to logical replication worker
> errcontext (proposed[2])
> C. Store error information (e.g., the error message and commit-LSN) to
> the system catalog
> D. Introduce ALTER SUBSCRIPTION SKIP
> E. Record the skipped data somewhere: server logs or a table
>
> Given the remaining time for PG15, it’s unlikely to complete all of
> them for PG15 by the feature freeze. The most realistic plan for PG15
> in my mind is to complete B and D. With these two items, the LSN of
> the error-ed transaction is shown in the server log, and we can ask
> users to check server logs for the LSN and use it with ALTER
> SUBSCRIPTION SKIP command.
>
It makes sense to me to try to finish B and D from the above list for
PG-15. I can review the patch for D in detail if others don't have an
objection to it.
Peter E., others, any opinion on this matter?
> If the community agrees with B+D, we will
> have a user-visible feature for PG15 which can be further
> extended/improved in PG16 by adding C and E.
Agreed.
>
> I've attached an updated patch for D and here is the summary:
>
> * Introduce a new command ALTER SUBSCRIPTION ... SKIP (lsn =
> '0/1234'). The user can get the commit-LSN of the transaction in
> question from the server logs thanks to B[2].
> * The user-specified LSN (say skip-LSN) is stored in the
> pg_subscription catalog.
> * The apply worker skips the whole transaction if the transaction's
> commit-LSN exactly matches to skip-LSN.
> * The skip-LSN has an effect on only the first non-empty transaction
> since the worker started to apply changes. IOW it's cleared after
> either skipping the whole transaction or successfully committing a
> non-empty transaction, preventing the skip-LSN to remain in the
> catalog. Also, since the latter case means that the user set the wrong
> skip-LSN we clear it with a warning.
>
As this will be displayed only in server logs and by background apply
worker, should it be LOG or WARNING?
--
With Regards,
Amit Kapila.
