Re: Assertion failure in SnapBuildInitialSnapshot()

On Fri, Nov 7, 2025 at 8:30 AM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> On Friday, November 7, 2025 2:36 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > On Thu, Nov 6, 2025 at 2:36 AM Amit Kapila <amit.kapila16@gmail.com>
> > wrote:
> > >
> > > Good point. This can happen when the last slot is invalidated or dropped.
> >
> > After the last slot is invalidated or dropped, both slot_xmin and
> > slot_catalog_xmin values are set InvalidTransactionId. Then in this
> > case, these values are ignored when computing the oldest safe decoding
> > XID in GetOldestSafeDecodingTransactionId(), no? Or do you mean that
> > there is a case where slot_xmin and slot_catalog_xmin retreat to a
> > valid XID?
>
> I think when replication_slot_xmin is invalid,
> GetOldestSafeDecodingTransactionId would return nextXid, which can be greater
> than the original snap.xmin if some transaction IDs have been assigned.
>

Won't we have a problem that values of
procArray->replication_slot_xmin and
procArray->replication_slot_catalog_xmin won't be set to
InvalidTransactionId after last slot removal due to a new check unless
we do special treatment for drop/invalidation of a slot? And that
would lead to accumulating dead rows even when not required.

--
With Regards,
Amit Kapila.