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

On Fri, Mar 8, 2024 at 8:08 PM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
>
> On Wed, Mar 6, 2024 at 4:28 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > IIUC, the current conflict_reason is primarily used to determine
> > logical slots on standby that got invalidated due to recovery time
> > conflict. On the primary, it will also show logical slots that got
> > invalidated due to the corresponding WAL got removed. Is that
> > understanding correct?
>
> That's right.
>
> > If so, we are already sort of overloading this
> > column. However, now adding more invalidation reasons that won't
> > happen during recovery conflict handling will change entirely the
> > purpose (as per the name we use) of this variable. I think
> > invalidation_reason could depict this column correctly but OTOH I
> > guess it would lose its original meaning/purpose.
>
> Hm. I get the concern. Are you okay with having inavlidation_reason
> separately for both logical and physical slots? In such a case,
> logical slots that got invalidated on the standby will have duplicate
> info in conflict_reason and invalidation_reason, is this fine?
>

If we have duplicate information in two columns that could be
confusing for users. BTW, isn't the recovery conflict occur only
because of rows_removed and wal_level_insufficient reasons? The
wal_removed or the new reasons you are proposing can't happen because
of recovery conflict. Am, I missing something here?

> Another idea is to make 'conflict_reason text' as a 'conflicting
> boolean' again (revert 007693f2a3), and have 'invalidation_reason
> text' for both logical and physical slots. So, whenever 'conflicting'
> is true, one can look at invalidation_reason for the reason for
> conflict. How does this sound?
>

So, does this mean that conflicting will only be true for some of the
reasons (say wal_level_insufficient, rows_removed, wal_removed) and
logical slots but not for others? I think that will also not eliminate
the duplicate information as user could have deduced that from single
column

--
With Regards,
Amit Kapila.