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From: shveta malik <shveta.malik@gmail.com>
Date: Thu, 23 Apr 2026 12:37:41 +0530
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 <CAJpy0uBWUR+nBfqHaDOwPAZvg7xT-9yEiYSwJVtp=vwVGJq_wA@mail.gmail.com>
Subject: Re: Warn on missing replica identity in CREATE/ALTER PUBLICATION
To: Chao Li <li.evan.chao@gmail.com>
Cc: =?UTF-8?B?5Y2X5ouT5byl?= <minamitakuya@lifull.com>,
	pgsql-hackers@lists.postgresql.org, shveta malik <shveta.malik@gmail.com>
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On Thu, Apr 23, 2026 at 12:21=E2=80=AFPM Chao Li <li.evan.chao@gmail.com> w=
rote:
>
>
>
> > On Apr 23, 2026, at 13:46, =E5=8D=97=E6=8B=93=E5=BC=A5 <minamitakuya@li=
full.com> wrote:
> >
> > # Reply draft v2 to Shveta
> >
> > ---
> >
> > Hi Shveta,
> >
> > Thanks for pointing out that thread. I've read through it carefully.
> >
> > I believe the two proposals address different aspects of the same
> > problem:
> >
> > - The fallback RI approach changes runtime behavior so that tables
> >  without a primary key can still replicate UPDATE/DELETE.
> > - This proposal simply warns at DDL time that a publication contains
> >  tables whose replica identity will cause UPDATE/DELETE to fail at
> >  replication time.
> >
> > A WARNING at publication creation time is useful regardless of whether
> > a fallback mechanism exists, because:
> >
> > - If a table has REPLICA IDENTITY DEFAULT with no primary key, it
> >  silently falls back to NOTHING. Combining that with a publication
> >  that publishes updates/deletes is guaranteed to fail at runtime.
> >  A WARNING at DDL time closes this gap.
> > - Even users who explicitly set REPLICA IDENTITY NOTHING and add the
> >  table to an update/delete publication would benefit from a reminder,
> >  since that combination cannot succeed.
> > - The WARNING does not change any existing behavior =E2=80=94 it only m=
akes
> >  the misconfiguration visible earlier.
> >
> > Notably, Euler mentioned in that thread [1] that he would "suggest a
> > way to disallow or add a warning message while creating the
> > publication or adding new tables", which is exactly what this proposal
> > does.
> >
> > That said, I see the two proposals as complementary. Should I continue
> > this as a separate thread, or would it be better to join the existing
> > discussion?
> >
> > I have a working patch covering all publication paths (FOR TABLE,
> > FOR TABLES IN SCHEMA, FOR ALL TABLES, ALTER PUBLICATION). Happy to
> > post it either way.
> >
> > [1] https://www.postgresql.org/message-id/a9da608f-24be-4213-a712-85928=
52d37f1%40app.fastmail.com
> >
>
> You are very welcome to join the thread, as the initiator of that thread.
>
> I am not personally against your idea of adding such a warning message, b=
ut I think it would be better to consider the two features together as a wh=
ole solution from a system perspective.
>
> In any case, new features will have to wait for v20 until July, so we sti=
ll have time for more discussion and deeper consideration.

I agree. But if the RI fallback option gets delayed due to lack of
consensus on the design or other reasons, issuing a WARNING during
publication creation seems like a reasonable approach.

thanks
Shveta