Re: Proposal: Conflict log history table for Logical Replication

Hi,

On Fri, Sep 12, 2025 at 3:13 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> I was looking into another thread where we provide an error table for
> COPY [1], it requires the user to pre-create the error table. And
> inside the COPY command we will validate the table, validation in that
> context is a one-time process checking for: (1) table existence, (2)
> ability to acquire a sufficient lock, (3) INSERT privileges, and (4)
> matching column names and data types. This approach avoids concerns
> about the user's DROP or ALTER permissions.
>
> Our requirement for the logical replication conflict log table
> differs, as we must validate the target table upon every conflict
> insertion, not just at subscription creation. A more robust
> alternative is to perform validation and acquire a lock on the
> conflict table whenever the subscription worker starts. This prevents
> modifications (like ALTER or DROP) while the worker is active. When
> the worker gets restarted, we can re-validate the table and
> automatically disable the conflict logging feature if validation
> fails.  And this can be enabled by ALTER SUBSCRIPTION by setting the
> option again.

Having to worry about ALTER/DROP and adding code to protect seems like
an overkill.

> And if we want in first version we can expect user to create the table
> as per the expected schema and supply it, this will avoid the need of
> handling how to avoid it from publishing as it will be user's
> responsibility and then in top up patches we can also allow to create
> the table internally if tables doesn't exist and then we can find out
> solution to avoid it from being publish when ALL TABLES are published.

This looks much more simple to start with.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com