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From: Chao Li <[email protected]>
To: 南拓弥 <[email protected]>
Cc: shveta malik <[email protected]>
Cc: [email protected]
Subject: Re: Warn on missing replica identity in CREATE/ALTER PUBLICATION
Date: Thu, 23 Apr 2026 14:50:22 +0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAP6NMUJEvkD1BKm8YCVch5YhcwqaVeLQXWGQhqF-+gdDufgs3w@mail.gmail.com>
References: <CAP6NMUKYgRJ3Z5ThhtXpYYkRBffT=fAStwQ3_1Cab0tREZ=5NQ@mail.gmail.com>
	<CAJpy0uAd2BY_jinMWscfLr11WHra7sxrNc18jKbkhp=4CkAFig@mail.gmail.com>
	<CAP6NMUJEvkD1BKm8YCVch5YhcwqaVeLQXWGQhqF-+gdDufgs3w@mail.gmail.com>



> On Apr 23, 2026, at 13:46, 南拓弥 <[email protected]> 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 — it only makes
>  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-a712-8592852d37f1%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, but I think it would be better to consider the two features together as a whole solution from a system perspective.

In any case, new features will have to wait for v20 until July, so we still have time for more discussion and deeper consideration.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/

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