Re: Newly created replication slot may be invalidated by checkpoint

From: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
To: "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Vitaly Davydov <v(dot)davydov(at)postgrespro(dot)ru>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "suyu(dot)cmj" <mengjuan(dot)cmj(at)alibaba-inc(dot)com>, tomas <tomas(at)vondra(dot)me>, michael <michael(at)paquier(dot)xyz>, "bharath(dot)rupireddyforpostgres" <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Subject: Re: Newly created replication slot may be invalidated by checkpoint
Date: 2025-12-18 12:11:24
Message-ID: CAPpHfdvL9ixox0aDf-Wqbtad3Xcf42x8a+fqcEPux=8pa0pCJA@mail.gmail.com
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On Thu, Dec 11, 2025 at 9:29 AM Zhijie Hou (Fujitsu)
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> On Thursday, December 11, 2025 3:09 PM Zhijie Hou (Fujitsu) <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> > I reviewed that approach, and I think the main distinction lies in whether to
> > use a new LWLock to serialize the process or rely on an existing lock.
> > Introducing a new LWLock in back branches would alter the size of
> > MainLWLockArray and affect
> > NUM_INDIVIDUAL_LWLOCKS/LWTRANCHE_FIRST_USER_DEFINED.
> > Although this may not directly impact user applications since users typically
> > use standard APIs like RequestNamedLWLockTranche and
> > LWLockNewTrancheId to add private LWLocks, it still has a slight risk.
> > Additionally, using an existing lock could keep code similarity with the HEAD,
> > which can be helpful for future bug fixes and analysis.
>
> BTW, I searched the git history and can only find 2 old commits that adds lwlock
> On stable branches, but both of are fixing serious problems such as
> data corruption / loss issues.

I understand that that was done due to more serious reasons than ours.
As I get, it run smoothly. At least, I can't remember we have been
reported with any issues regarding to this change. Can we assume this
is kind of "tested" and add new LWLock to both master and back
branches? I think this would be good in terms of clarity and minimal
possible divergence of back branches.

------
Regards,
Alexander Korotkov
Supabase

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