Re: Minimal logical decoding on standbys

On Tue, Apr 4, 2023 at 6:05 PM Drouvot, Bertrand
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> On 4/4/23 1:43 PM, Amit Kapila wrote:
> > On Tue, Apr 4, 2023 at 3:14 PM Drouvot, Bertrand
> > <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> >>
> >
> >
> > +static inline bool
> > +LogicalReplicationSlotXidsConflict(ReplicationSlot *s, TransactionId xid)
> > +{
> > + TransactionId slot_xmin;
> > + TransactionId slot_catalog_xmin;
> > +
> > + slot_xmin = s->data.xmin;
> > + slot_catalog_xmin = s->data.catalog_xmin;
> > +
> > + return (((TransactionIdIsValid(slot_xmin) &&
> > TransactionIdPrecedesOrEquals(slot_xmin, xid)) ||
> >
> > For logical slots, slot->data.xmin will always be an
> > InvalidTransactionId. It will only be set/updated for physical slots.
> > So, it is not clear to me why in this and other related functions, you
> > are referring to and or invalidating it.
> >
>
> I think you're right that invalidating/checking only on the catalog xmin is
> enough for logical slot (I'm not sure how I ended up taking the xmin into account but
> that seems useless indeed).
>

I think we might want to consider slot's effective_xmin instead of
data.xmin as we use that to store xmin_horizon when we build the full
snapshot.

--
With Regards,
Amit Kapila.