Re: Doc: fix the note related to the GUC "synchronized_standby_slots"

On Mon, Aug 26, 2024 at 6:38 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> On Monday, August 26, 2024 5:37 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Mon, Aug 26, 2024 at 1:30 PM <Masahiro.Ikeda@nttdata.com> wrote:
> > >
> > > When I read the following documentation related to the
> > "synchronized_standby_slots", I misunderstood that data loss would not occur
> > in the case of synchronous physical replication. However, this is incorrect (see
> > reproduce.txt).
> > >
> > > > Note that in the case of asynchronous replication, there remains a risk of
> > data loss for transactions committed on the former primary server but have yet
> > to be replicated to the new primary server.
> > > https://www.postgresql.org/docs/17/logical-replication-failover.html
> > >
> > > Am I missing something?
> > >
> >
> > It seems part of the paragraph: "Note that in the case of asynchronous
> > replication, there remains a risk of data loss for transactions committed on the
> > former primary server but have yet to be replicated to the new primary server." is
> > a bit confusing. Will it make things clear to me if we remove that part?
>
> I think the intention is to address a complaint[1] that the date inserted on
> primary after the primary disconnects with the standby is still lost after
> failover. But after rethinking, maybe it's doesn't directly belong to the topic in
> the logical failover section because it's a general fact for async replication.
> If we think it matters, maybe we can remove this part and slightly modify
> another part:
>
>    parameter ensures a seamless transition of those subscriptions after the
>    standby is promoted. They can continue subscribing to publications on the
> -   new primary server without losing data.
> +   new primary server without losing that has already been replicated and
> +    flushed on the standby server.
>

Yeah, we can change that way but not sure if that satisfies the OP's
concern. I am waiting for his response.

--
With Regards,
Amit Kapila.