Re: Skipping logical replication transactions on subscriber side

On Thu, Jul 8, 2021 at 6:28 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Jul 7, 2021 at 11:47 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Tue, Jul 6, 2021 at 6:33 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > >
> > > > According to the doc, ALTER SUBSCRIPTION ... SET is used to alter
> > > > parameters originally set by CREATE SUBSCRIPTION. Therefore, we can
> > > > specify a subset of parameters that can be specified by CREATE
> > > > SUBSCRIPTION. It makes sense to me for 'disable_on_error' since it can
> > > > be specified by CREATE SUBSCRIPTION. Whereas SKIP TRANSACTION stuff
> > > > cannot be done. Are you concerned about adding a syntax to ALTER
> > > > SUBSCRIPTION?
> > > >
> > >
> > > Both for additional syntax and consistency with disable_on_error.
> > > Isn't it just a current implementation that Alter only allows to
> > > change parameters supported by Create? Is there a reason why we can't
> > > allow Alter to set/change some parameters not supported by Create?
> >
> > I think there is not reason for that but looking at ALTER TABLE I
> > thought there is such a policy.
> >
>
> If we are looking for precedent then I think we allow to set
> configuration parameters via Alter Database but not via Create
> Database. Does that address your concern?

Thank you for the info! But it seems like CREATE DATABASE doesn't
support SET in the first place. Also interestingly, ALTER SUBSCRIPTION
support both ENABLE/DISABLE and SET (enabled = on/off). I’m not sure
from the point of view of consistency with other CREATE, ALTER
commands, and disable_on_error but it might be better to avoid adding
additional syntax.

>
> > I thought the skipping transaction
> > feature is somewhat different from disable_on_error feature. The
> > former seems a feature to deal with a problem on the spot whereas the
> > latter seems a setting of a subscription. Anyway, if we use the
> > subscription option, we can reset the XID by setting 0? Or do we need
> > ALTER SUBSCRIPTION RESET?
>
> The other commands like Alter Table, Alter Database, etc, which
> provides a way to Set some parameter/option, have a Reset variant. I
> think it would be good to have it for Alter Subscription as well but
> we might want to allow other parameters to be reset by that as well.

Agreed.

Regards,

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