RE: "out of relcache_callback_list slots" after multiple calls to pg_logical_slot_get_binary_changes

On Mon, Feb 20, 2023 11:31 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
> > I'm pretty sure that everytime an output plugin is initialized on a
> > process, it installs the same set of syscache/relcache callbacks each
> > time. Do you think we could simply stop duplicate registration of
> > those callbacks by using a static boolean? It would be far simpler.
>
> Yeah, I think that's the way it's done elsewhere. Removing and
> re-registering your callback seems expensive, and it also destroys
> any reasoning that anyone might have made about the order in which
> different callbacks will get called. (Admittedly, that's probably not
> important for invalidation callbacks, but it does matter for e.g.
> process exit callbacks.)
>

Thanks for your reply. I agree that's expensive. Attach a new patch which adds a
static boolean to avoid duplicate registration.

Regards,
Shi Yu