Thanks for this feedback,
I'll remove the check on the sync_replication_slots parameter.
I think it is interesting as you suggest to start with the idea of the
pg_alter_replication_slot API, I will make a new proposal by opening a new
thread, hoping to be supported in my approach. Is there already an
initiative about the pg_drop_all_slots API?
Best Regards,
Fabrice
On Sun, Jul 13, 2025 at 1:30 PM Amit Kapila <amit.kapil...@gmail.com> wrote:
> On Fri, Jul 11, 2025 at 8:42 PM Fabrice Chapuis <fabrice636...@gmail.com>
> wrote:
> >
> > Hi Amit,
> > Here is a proposed solution to handle the problem of creating the
> logical replication slot on standby after a switchover.
> > Thank you for your comments and help on this issue
> >
> > Regards
> >
> > Fabrice
> >
> > diff --git a/src/backend/replication/logical/slotsync.c
> b/src/backend/replication/logical/slotsync.c
> > index 656e66e..296840a 100644
> > --- a/src/backend/replication/logical/slotsync.c
> > +++ b/src/backend/replication/logical/slotsync.c
> > @@ -627,6 +627,7 @@ synchronize_one_slot(RemoteSlot *remote_slot, Oid
> remote_dbid)
> > ReplicationSlot *slot;
> > XLogRecPtr latestFlushPtr;
> > bool slot_updated = false;
> > + bool overwriting_failover_slot = true; /* could be a
> GUC */
> >
> > /*
> > * Make sure that concerned WAL is received and flushed before
> syncing
> > @@ -654,19 +655,37 @@ synchronize_one_slot(RemoteSlot *remote_slot, Oid
> remote_dbid)
> > if ((slot = SearchNamedReplicationSlot(remote_slot->name, true)))
> > {
> > bool synced;
> > + bool failover_status = remote_slot->failover;;
> >
> > SpinLockAcquire(&slot->mutex);
> > synced = slot->data.synced;
> > SpinLockRelease(&slot->mutex);
> >
> > - /* User-created slot with the same name exists, raise
> ERROR. */
> > - if (!synced)
> > - ereport(ERROR,
> > + if (!synced){
> > + /*
> > + * Check if we need to overwrite an existing
> failover slot and
> > + * if slot has the failover flag set to true
> > + * and the sync_replication_slots is on,
> > + * other check could be added here */
> > + if (overwriting_failover_slot && failover_status
> && sync_replication_slots){
> > +
>
> I think we don't need to explicitly check sync_replication_slots, as
> we should reach here only when that flag is set. I think we should
> introduce an pg_alter_replication_slot which allows to overwrite
> existing slots during sync by setting a parameter like allow_overwrite
> (or something like that). This API will be useful for other purposes,
> like changing two_phase or failover properties of the slot after the
> creation of the slot. BTW, we also discussed supporting
> pg_drop_all_slots kind of API as well. See if you are interested in
> implementing that API as well.
>
> Note: I suggest starting a new thread with the concrete proposal for
> the new API or GUC, stating how it will be helpful. It might help in
> getting suggestions from others as well.
>
> --
> With Regards,
> Amit Kapila.
>
