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

On Sat, Feb 8, 2025 at 12:28 PM Zhijie Hou (Fujitsu)
<houzj(dot)fnst(at)fujitsu(dot)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.

> 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?

> 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.

--
With Regards,
Amit Kapila.