Re: Synchronizing slots from primary to standby - Mailing list pgsql-hackers

From Bertrand Drouvot
Subject Re: Synchronizing slots from primary to standby
Date
Msg-id ZZ+dmz/myfv2TGp8@ip-10-97-1-34.eu-west-3.compute.internal
Whole thread Raw
In response to RE: Synchronizing slots from primary to standby  ("Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>)
Responses Re: Synchronizing slots from primary to standby
List pgsql-hackers
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@gmail.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



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