Re: Add contrib/pg_logicalsnapinspect

On Wed, Aug 28, 2024 at 1:25 AM Bertrand Drouvot
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> On Mon, Aug 26, 2024 at 07:05:27PM +0530, Amit Kapila wrote:
> > On Thu, Aug 22, 2024 at 5:56 PM Bertrand Drouvot
> > <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> > >
> > > 2. The SnapBuildOnDisk and SnapBuild structs are now exposed to public. Means
> > > we should now pay much more attention when changing their contents but I think
> > > it's worth it.
> > >
> >
> > Is it possible to avoid exposing these structures? Can we expose some
> > function from snapbuild.c that provides the required information?
>
> Yeah, that's an option if we don't want to expose those structs to public.
>
> I think we could 1/ create a function that would return a formed HeapTuple, or
> 2/ we could create multiple functions (about 15) that would return the values
> we are interested in.
>
> I think 2/ is fine as it would give more flexiblity (no need to retrieve a whole
> tuple if one is interested to only one value).
>

True, but OTOH, each time we add a new field to these structures, a
new function has to be exposed. I don't have a strong opinion on this
but seeing current use cases, it seems okay to expose a single
function.

> What do you think? Did you have something else in mind?
>

On similar lines, we can also provide a function to get the slot's
on-disk data. IIRC, Bharath had previously proposed a tool to achieve
the same. It is fine if we don't want to add that as part of this
patch but I mentioned it because by having that we can have a set of
functions to view logical decoding data.

--
With Regards,
Amit Kapila.