Re: Synchronizing slots from primary to standby

Hi,

On Wed, Jan 10, 2024 at 12:23:14PM +0000, Zhijie Hou (Fujitsu) wrote:
> On Wednesday, January 10, 2024 2:26 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
> > + LogicalConfirmReceivedLocation(remote_slot->confirmed_lsn);
> > + LogicalIncreaseXminForSlot(remote_slot->confirmed_lsn,
> > + remote_slot->catalog_xmin);
> > + LogicalIncreaseRestartDecodingForSlot(remote_slot->confirmed_lsn,
> > + remote_slot->restart_lsn);
> > +}
> >
> > IIUC on the standby we just want to overwrite what we get from primary no? If
> > so why we are using those APIs that are meant for the actual decoding slots
> > where it needs to take certain logical decisions instead of mere overwriting?
>
> I think we don't have a strong reason to use these APIs, but it was convenient to
> use these APIs as they can take care of updating the slots info and will call
> functions like, ReplicationSlotsComputeRequiredXmin,
> ReplicationSlotsComputeRequiredLSN internally. Or do you prefer directly overwriting
> the fields and call these manually ?

I'd vote for using the APIs as I think it will be harder to maintain if we are
not using them (means ensure the "direct" overwriting still makes sense over time).

FWIW, pg_failover_slots also rely on those APIs from what I can see.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com