Re: replication_origin and replication_origin_lsn usage on subscriber

On Tue, Jul 14, 2020 at 12:05 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Tue, Jul 14, 2020 at 11:14 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Tue, Jul 14, 2020 at 11:00 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> > >
> > > On Thu, Jul 9, 2020 at 6:55 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > >
> > > > On Thu, Jul 9, 2020 at 6:14 PM Petr Jelinek <petr(at)2ndquadrant(dot)com> wrote:
> > > > >
> > > > >
> > > > > If we were to support the origin forwarding, then strictly speaking we
> > > > > need everything only at commit time from correctness perspective,
> > > > >
> > > >
> > > > Okay. Anyway streaming mode is optional, so in such cases, we can keep it 'off'
> > > >
> > > > > but
> > > > > ideally origin_id would be best sent with first message as it can be
> > > > > used to filter out changes at decoding stage rather than while we
> > > > > process the commit so having it set early improves performance of decoding.
> > > > >
> > > >
> > > > Yeah, makes sense. So, we will just send origin_id (with first
> > > > streaming start message) and leave others.
> > >
> > > So IIUC, currently we are sending the latest origin_id which is set
> > > during the commit time. So in our case, while we start streaming we
> > > will send the origin_id of the latest change in the current stream
> > > right?
> > >
> >
> > It has to be sent only once with the first start message not with
> > consecutive start messages.
>
> Okay, so do you mean to say that with the first start message we send
> the origin_id of the latest change?
>

Yes.

> because during the transaction
> lifetime, the origin id can be changed.
>

Yeah, it could be changed but if we have to send again apart from with
the first message then it should be sent with each message. So, I
think it is better to just send it once during the transaction as we
do it now (send with begin message).

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com