Re: Add a hook for handling logical decoding messages on subscribers.

On Thu, Jul 9, 2026 at 5:14 AM Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>
> On Wed, Jun 24, 2026 at 3:02 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > Right. I'm implementing a basic DDL replication solution using this
> > hook as a sample implementation. Other than that, this feature can be
> > used to add additional information for the replicated transaction that
> > is not replicated via logical replication protocol, such as the
> > executed user or context-specific information, which can then be
> > dispatched to a CDC system connected to the subscriber.
>
> +1 for the proposed hook, although I haven't read the patch yet.
>
> I know of a system that uses logical decoding messages to propagate data
> to external systems. In that system, the application writes the data to
> be propagated as logical decoding messages, and a CDC pipeline consumes
> them via logical decoding and sends them to other systems, for example
> through Kafka.
>
> In that system, when the remote site is maintained by physical replication,
> the same logical decoding messages can be decoded on the standby
> at the remote site to deliver them to external systems there. However,
> if the remote site uses logical replication instead, those messages are
> currently neither delivered to nor processed on the subscriber at
> the remote site. As a result, the CDC pipeline at the remote site cannot
> consume the data they carry.
>
> The proposed hook might be useful for this use case. An extension could
> process the incoming logical decoding messages on the subscriber and
> forward them to the local CDC pipeline, or store or re-emit them in a form
> that local consumers can process.

Thank you for sharing the concrete use case. This is one of the use
cases I initially imagined.

I've rebased and updated the patch. Please review it.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com