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Subject: Re: Improve logical replication usability when tables lack primary
 keys
From: Chao Li <li.evan.chao@gmail.com>
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Date: Tue, 11 Nov 2025 20:40:39 +0800
Cc: Postgres hackers <pgsql-hackers@lists.postgresql.org>
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To: Amit Kapila <amit.kapila16@gmail.com>
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Hi Amit,

Thanks for asking.

> On Nov 11, 2025, at 19:18, Amit Kapila <amit.kapila16@gmail.com> =
wrote:
>=20
> On Mon, Nov 10, 2025 at 1:36=E2=80=AFPM Chao Li =
<li.evan.chao@gmail.com> wrote:
>>=20
>> * BACKGROUND
>>=20
>> This requirement comes from several users operating large =
deployments, particularly in HIS (Hospital Information Systems). The =
situation can be summarized as follows:
>>=20
>> - A central DB operations team maintains the main database and =
configures logical replication for all tables.
>> - Multiple third-party application vendors are allowed to create new =
tables in that database.
>> - Some of these newly created tables lack a primary key. Since =
logical replication with `REPLICATION IDENTITY DEFAULT` requires a =
primary key, such tables silently fail to replicate.
>> - The DB operations team must then spend significant effort =
identifying the affected tables and correcting them manually.
>>=20
>=20
> Can you share an example of how we silently fail to replicate? Won't
> in such cases UPDATE/DELETE will anyway raise an ERROR?
>=20

Yes, UPDATE/DELETE will fail. That=E2=80=99s the easy case to expose the =
error. Actually my patch will allow the update/delete.

However, some tables, like dictionary tables, they are important, but =
don=E2=80=99t have much update/delete, they may silently fail to =
replicate.

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