Re: Add contrib/pg_logicalsnapinspect

On Tue, Sep 10, 2024 at 8:56 PM Bertrand Drouvot
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> On Mon, Sep 09, 2024 at 04:24:09PM +0530, Amit Kapila wrote:
> > On Fri, Aug 30, 2024 at 5:18 PM Bertrand Drouvot
> > <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> > > as we decided not to expose the SnapBuildOnDisk and SnapBuild structs to public
> > > and to create/expose 2 new functions in snapbuild.c then the functions in the
> > > module would do nothing but expose the data coming from the snapbuild.c's
> > > functions (get the tuple and send it to the client). That sounds weird to me to
> > > create a module that would "only" do so, that's why I thought that in core
> > > functions taking care of everything make more sense.
> > >
> >
> > I see your point. Does anyone else have an opinion on the need for
> > these functions and whether to expose them from a contrib module or
> > have them as core functions?
>
> I looked at when the SNAPBUILD_VERSION has been changed:
>
> ec5896aed3 (2014)
> a975ff4980 (2021)
> 8bdb1332eb (2021)
> 7f13ac8123 (2022)
> bb19b70081 (2024)
>
> So it's not like we are changing the SnapBuildOnDisk or SnapBuild structs that
> frequently. Furthermore, those structs are serialized and so we have to preserve
> their on-disk compatibility (means we can change them only in a major release
> if we need to).
>
> So, I think it would not be that much of an issue to expose those structs and
> create a new contrib module (as v1 did propose) instead of in core new functions.
>
> If we want to insist that external modules "should" not rely on those structs then
> we could put them into a new internal_snapbuild.h file (instead of snapbuild.h
> as proposed in v1).
>

Adding snapbuild_internal.h sounds like a good idea.

> At the end, I think that creating a contrib module and exposing those structs in
> internal_snapbuild.h make more sense (as compared to in core functions).
>

Fail enough. We can keep the module name as logicalinspect so that we
can extend it for other logical decoding/replication-related files in
the future.

--
With Regards,
Amit Kapila.