Re: Skipping logical replication transactions on subscriber side

On Thu, Jan 27, 2022 at 10:42 PM Peter Eisentraut
<peter(dot)eisentraut(at)enterprisedb(dot)com> wrote:
>
> On 26.01.22 05:05, Masahiko Sawada wrote:
> >> I think it is okay to clear after the first successful application of
> >> any transaction. What I was not sure was about the idea of giving
> >> WARNING/ERROR if the first xact to be applied is not the same as
> >> skip_xid.
> > Do you prefer not to do anything in this case?
>
> I think a warning would be sensible. If the user specifies to skip a
> certain transaction and then that doesn't happen, we should at least say
> something.

Meanwhile waiting for comments on the discussion about the designs of
both pg_stat_subscription_workers and ALTER SUBSCRIPTION SKIP feature,
I’ve incorporated some (minor) comments on the current design patch,
which includes:

* Use LSN instead of XID.
* Raise a warning if the user specifies to skip a certain transaction
and then that doesn’t happen.
* Skip-LSN has an effect on the first non-empty transaction. That is,
it’s cleared after successfully committing a non-empty transaction,
preventing the user-specified wrong LSN to remain.
* Remove some unnecessary tap tests to reduce the test time.

I think we all agree with the first point regardless of where we store
error information. And speaking of the current design, I think we all
agree on other points. Since the design discussion is ongoing, I’ll
incorporate other comments according to the result of the discussion.

The attached 0001 patch modifies the pg_stat_subscription_workers to
report LSN instead of XID, which is required by ALTER SUBSCRIPTION
SKIP patch, the 0002 patch.

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/