RE: Introduce XID age and inactive timeout based replication slot invalidation

On Monday, February 10, 2025 2:10 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Sat, Feb 8, 2025 at 12:28 PM Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>
> wrote:
> >
> > 3.
> >
> > +                       if (cause & RS_INVAL_HORIZON)
> > +                       {
> > +                               if (!SlotIsLogical(s))
> > +                                       goto invalidation_marked;
> >
> > I am not sure if this logic is correct. Even if the slot would not be
> > invalidated due to RS_INVAL_HORIZON, we should continue to check other
> causes.
> >
> 
> Isn't this comment apply to even the next condition (if (dboid != InvalidOid &&
> dboid != s->data.database))? We need to probably continue to check other
> invalidation causes unless one is set.

Yes, both places need to be fixed.

> 
> > Besides, instead of using a goto, I personally prefer to move all
> > these codes into a separate function which would return a single invalidation
> cause.
> >
> 
> Instead of using goto label (invalidation_marked:), won't it be better if we use a
> boolean invalidation_marked and convert all if's to if ..
> else if .. else cases?

Yes, I think that would be better.

> 
> > 4.
> > -       if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED,
> > +       if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED
> |
> > + RS_INVAL_IDLE_TIMEOUT,
> >
> _logSegNo, InvalidOid,
> >
> > InvalidTransactionId))
> >
> > I think this change could trigger an unnecessary WAL position
> > re-calculation when slots are invalidated only due to
> RS_INVAL_IDLE_TIMEOUT.
> >
> 
> Why is that unnecessary? If some slots got invalidated due to timeout, we don't
> want to retain the WAL corresponding to them.

Sorry, I mistakenly thought that the slot only protected dead tuples.
Please disregard this comment.

Best Regards,
Hou zj