Re: Aggregate Push Down - Performing aggregation on foreign server - Mailing list pgsql-hackers

On Tue, Aug 30, 2016 at 6:51 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:

Hi

2016-08-30 15:02 GMT+02:00 Jeevan Chalke <jeevan.chalke@enterprisedb.com>:

Hi all,

Attached is the patch which adds support to push down aggregation and grouping
to the foreign server for postgres_fdw. Performing aggregation on foreign
server results into fetching fewer rows from foreign side as compared to
fetching all the rows and aggregating/grouping locally. Performing grouping on
foreign server may use indexes if available. So pushing down aggregates/
grouping on foreign server performs better than doing that locally. (Attached
EXPLAIN output for few simple grouping queries, with and without push down).

is it work without FDW too?. It can be pretty interesting too.

No. Aggrgate push down is supported through the GetForeignUpperPaths() hook
added for postgres_fdw. Thus it works only with postgres_fdw.

Do you mean whether this works with any extensions via implementing
create_upper_paths_hook() function?
The answer is No. This patch does not touch this hook.

 

Regards

Pavel

 

Thanks

--

Jeevan B Chalke
Principal Software Engineer, Product Development
EnterpriseDB Corporation
The Enterprise PostgreSQL Company