WIP: Aggregation push-down - take2

Hi everyone.

I develop postgresql's extension such as fdw in my work.
I'm interested in using postgresql for OLAP.
After [1] having been withdrawn, I reviewed [1].
I think that this patch is realy useful when using OLAP queries.
Furthermore, I think it would be more useful if this patch works on a foreign table.
So, I would like to ask you a question on this patch in this new thread.

I changed this patch a little and confirmed that my idea is true.
The followings are things I found and differences of between my prototype and this patch.
  1. Things I found
   I execute a query which contain join of postgres_fdw's foreign table and a table and aggregation of the join result.
   In my setting, my prototype reduce this query's response by 93%.
  2. Differences between my prototype and this patch
   (1) Pushdown aggregation of foeign table if FDW pushdown partial aggregation
   (2) postgres_fdw pushdowns some partial aggregations
I attached my prototype source code and content of my experiment.
I want to resume development of this patch if there is some possibility of accept of this patch's function.
I took a contact to Mr.Houska on resuming development of this patch.
As a result, Mr.Houska advised for me that I ask in pgsql-hackers whether any reviewers / committers are
interested to work on the patch.
Is anyone interested in my work?

Sincerely yours.
Yuuki Fujii

[1] https://commitfest.postgresql.org/32/

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Yuuki Fujii
Information Technology R&D Center Mitsubishi Electric Corporation