Re: Synchronizing slots from primary to standby

Hi,

On Fri, Feb 23, 2024 at 08:35:44AM +0530, shveta malik wrote:
> On Thu, Feb 22, 2024 at 4:35 PM Bertrand Drouvot
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> >
> > Suppose that in synchronize_slots() the query would be:
> >
> > const char *query = "SELECT slot_name, plugin, confirmed_flush_lsn,"
> > " restart_lsn, catalog_xmin, two_phase, failover,"
> > " database, conflict_reason"
> > " FROM pg_catalog.pg_replication_slots"
> > " WHERE failover and NOT temporary and 1 = 1";
> >
> > Then my comment is to rewrite it to:
> >
> > const char *query = "SELECT slot_name, plugin, confirmed_flush_lsn,"
> > " restart_lsn, catalog_xmin, two_phase, failover,"
> > " database, conflict_reason"
> > " FROM pg_catalog.pg_replication_slots"
> > " WHERE failover and NOT temporary and 1 OPERATOR(pg_catalog.=) 1";
> >
> > to ensure the operator "=" is coming from the pg_catalog schema.
> >
>
> Thanks for the details, but slot-sync does not use SPI calls, it uses
> libpqrcv calls.

Sorry for the confusion, I meant to say "remote SQL calls".

> So is this change needed?

The example I provided is a "fake" one (as currently the "=" operator is not
used in the const char *query in synchronize_slots()). So there is currently
nothing to change here. I just want to highlight that if we are using (or will
use) operators in the remote SQL calls then we should ensure they are coming from
the pg_catalog schema (as in the example provided above).

Regards,

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