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From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Mon, 6 Apr 2026 01:44:52 -0700
Message-ID: 
 <CAD21AoArh6-RfOGGY6GfWqqHv0qUJEMwXVmGQk=29uYiKFLSgA@mail.gmail.com>
Subject: Re: Introduce XID age based replication slot invalidation
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
	SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>,
	"Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>,
 John H <johnhyvr@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
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On Sun, Apr 5, 2026 at 7:52=E2=80=AFPM Bharath Rupireddy
<bharath.rupireddyforpostgres@gmail.com> wrote:
>
> Hi,
>
> On Sun, Apr 5, 2026 at 1:03=E2=80=AFAM Masahiko Sawada <sawada.mshk@gmail=
.com> wrote:
> >
> > Thank you for updating the patch!
> >
> > I've made some changes including moving MaybeInvalidateXidAgedSlot()
> > to vacuum.c since the function seems more inherently tied to vacuum
> > context. Also, updated the commit message and fixed typos.
> >
> > Please review the attached patch.
>
> Thank you Sawada-san!
>
> I took a look at the v10 patch and it LGTM. I tested it - make
> check-world passes, pgindent doesn't complain.
>

While reviewing the patch, I found that with this patch, backend
processes and autovacuum workers can simultaneously attempt to
invalidate the same slot for the same reason. When invalidating a
slot, we send a signal to the process owning the slot and wait for it
to exit and release the slot. If the process takes a long time to exit
for some reason, subsequent autovacuum workers attempting to
invalidate the same slot will also send a SIGTERM and get stuck at
InvalidatePossiblyObsoleteSlot(). In the worst case, this could result
in all autovacuum activity being blocked. I think we need to address
this problem.

Regards,

--=20
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com