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

Hi,

On Thu, Aug 6, 2026 at 9:59 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> > 2/
> > + /*
> > + * The message doesn't belong to any remote transaction, so there is
> > + * no remote commit LSN nor timestamp to record. Clear the state left
> > + * over by the previously applied transaction so that this commit
> > + * doesn't inherit it.
> > + */
> > + replorigin_xact_clear(false);
> >
> > Why is this a problem if we let the non-transactional message inherit it?
>
> IIUC non-transactional messages would have the same commit timestamp
> as the previously applied transaction, which is wrong to me.

Having replorigin_xact_clear there looks fine to me. The next
transaction commit would anyway set the origin LSN and timestamp.

> > Wrapping the hook with begin and end replication step is nice. This
> > lets the hook see the correct command ID, snapshot, and memory
> > context. There are callers that do the begin first and read message
> > next (insert), but it seems okay this way because read message doesn't
> > do any catalog or table accesses, so it should be fine.
> >
>
> begin_replication_step() switches the memory context to
> ApplyMessageContext. Given logicalrep_read_message() palloc's for
> messages, it should be called after begin_replication_step(). Fixed it.

Right. I verified other places and wherever the read does a palloc, it
is wrapped within begin and end replication step.

> I've attached the updated patch.

Thanks. The v4 patch looks good to me. pgindent and tests are happy. I
have no further comments. I marked the CF entry RfC
(https://commitfest.postgresql.org/patch/7092/) FWIW, the CF bot
complains with "needs rebase":
https://cfbot.cputube.org/patch_7092.log.

--
Bharath Rupireddy
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