Horton

Re: Improve logical replication usability when tables lack primary keys

Chao Li <li.evan.chao@gmail.com>

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From: Chao Li <li.evan.chao@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-12-15T03:35:36Z
Lists: pgsql-hackers

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add the notion of REPLICA IDENTITY for a table.


> On Dec 15, 2025, at 11:28, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> 
> On Tue, Nov 11, 2025 at 6:11 PM Chao Li <li.evan.chao@gmail.com> wrote:
>> 
>> Hi Amit,
>> 
>> Thanks for asking.
>> 
>>> On Nov 11, 2025, at 19:18, Amit Kapila <amit.kapila16@gmail.com> wrote:
>>> 
>>> On Mon, Nov 10, 2025 at 1:36 PM Chao Li <li.evan.chao@gmail.com> wrote:
>>>> 
>>>> * BACKGROUND
>>>> 
>>>> This requirement comes from several users operating large deployments, particularly in HIS (Hospital Information Systems). The situation can be summarized as follows:
>>>> 
>>>> - 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.
>>>> 
>>> 
>>> Can you share an example of how we silently fail to replicate? Won't
>>> in such cases UPDATE/DELETE will anyway raise an ERROR?
>>> 
>> 
>> Yes, UPDATE/DELETE will fail. That’s 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’t have much update/delete, they may silently fail to replicate.
> 
> But other than UPDATE/DELETE for what operation we need RI, I mean
> INSERT would work without any RI and UPDATE/DELETE will fail on the
> publisher itself without setting RI, so can you explain the exact case
> where it will silently fail to replicate?
> 
> -- 
> Regards,
> Dilip Kumar
> Google

Hi Dilip,

Thanks for asking. When fallback to FULL, UPDATE/DELETE will be allowed in the publisher side. In my first email, attached v1 patch is a PoC that has implemented the logic.

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