Re: Placement of synchronized_standby_slots description in config.sgml

On Thu, Feb 5, 2026 at 3:47 PM Shinya Kato <shinya11(dot)kato(at)gmail(dot)com> wrote:
>
> On Fri, Jan 23, 2026 at 7:22 PM Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> >
> > Hi,
> >
> > synchronized_standby_slots is defined in guc_parameter.dat as part of
> > the REPLICATION_PRIMARY group and appears under the "Primary Server"
> > section in postgresql.conf.sample. However, in the documentation
> > its description is placed under the "Sending Servers" section.
> >
> > Given this, it seems the description should also be under "Primary Server"
> > in the documentation. I've attached a patch that moves it there.
>
> Thank you for the patch! The patch LGTM.

Thanks for the review! I've pushed the patch.

> > Alternatively, if synchronized_standby_slots is intended to be set also
> > on a standby in cascading replication setups, then the current documentation
> > placement may be correct, and instead guc_parameter.dat and
> > postgresql.conf.sample should be updated. My understanding, though,
> > is that this parameter is normally set only on the primary. Right?
>
> You're right. PhysicalWakeupLogicalWalSnd() in walsender.c has this check:
>
> /*
> * If we are running in a standby, there is no need to wake up walsenders.
> * This is because we do not support syncing slots to cascading standbys,
> * so, there are no walsenders waiting for standbys to catch up.
> */
> if (RecoveryInProgress())
> return;
>
> So this parameter is only meaningful on the primary.

Thanks for confirming this!

Regards,

--
Fujii Masao