Re: Feedback on table expansion hook (including patch)

On Wed, May 12, 2021 at 04:48:29PM +0900, yuzuko wrote:
> Hello,
>
> > Thank you all for the feedback and insights.
> >
> > Yes, the intention is to *replace* expand_inherited_rtentry() in the same way planner_hook replaces standard_planner().
> >
>
> This patch is really useful. We are working on developing hypothetical
> partitioning as a feature of HypoPG[1][2], but we hit the same problem
> as TimescaleDB. Therefore we would also be thrilled to have that hook.
>
> Hypothetical partitioning allows users to define multiple partitioning
> schemes on real tables and real data hypothetically, and shows resulting
> queries' plan/cost with EXPLAIN using hypothetical partitioning schemes.
> Users can quickly check how their queries would behave if some tables
> were partitioned, and try different partitioning schemes. HypoPG does
> table expansion again according to the defined hypothetical partitioning
> schemes. For this purpose, we used get_relation_info hook, but in PG12,
> table expansion was moved, so we cannot do that using
> get_relation_info hook. This is exactly the same problem Erik has.
> Therefore the proposed hook would allow us to support hypothetical partitioning.

Sorry for missing that thread until now. And yes as Hosoya-san just mentioned,
we faced the exact same problem when implementing hypothetical partitioning,
and eventually had to stop as the changes in pg12 prevented it. So +1 for
introducing such a hook, it would also be useful for that usecase.