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

Hi,

On Fri, Mar 22, 2024 at 06:02:11PM +0530, Amit Kapila wrote:
> On Fri, Mar 22, 2024 at 5:30 PM Bertrand Drouvot
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> > On Fri, Mar 22, 2024 at 03:56:23PM +0530, Amit Kapila wrote:
> > > >
> > > > That would avoid testing twice "slot->data.persistency == RS_PERSISTENT".
> > > >
> > >
> > > That sounds like a good idea. Also, don't we need to consider physical
> > > slots where we don't reserve WAL during slot creation? I don't think
> > > there is a need to set inactive_at for such slots.
> >
> > If the slot is not active, why shouldn't we set inactive_at? I can understand
> > that such a slots do not present "any risks" but I think we should still set
> > inactive_at (also to not give the false impression that the slot is active).
> >
>
> But OTOH, there is a chance that we will invalidate such slots even
> though they have never reserved WAL in the first place which doesn't
> appear to be a good thing.

That's right but I don't think it is not a good thing. I think we should treat
inactive_at as an independent field (like if the timeout one does not exist at
all) and just focus on its meaning (slot being inactive). If one sets a timeout
(> 0) and gets an invalidation then I think it works as designed (even if the
slot does not present any "risk" as it does not hold any rows or WAL).

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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