Re: Aggregate Push Down - Performing aggregation on foreign server

On 2016/08/31 16:42, Pavel Stehule wrote:
> 2016-08-31 9:00 GMT+02:00 Robert Haas <robertmhaas(at)gmail(dot)com>:
>
>> On Wed, Aug 31, 2016 at 11:56 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
>> wrote:
>>> It is pity - lot of performance issues are related to this missing
>> feature.
>>
>> I don't think you are being very clear about what feature you are
>> talking about. The feature that Jeevan has implemented is pushing
>> aggregates to the remote side when postgres_fdw is in use. The
>> feature you are talking about is evidently something else, but you
>> haven't really said what it is. Or not in a way that I can
>> understand.
>>
>
> yes, It is not clear if FDW aggregate push down can be implemented together
> with internal aggregate push down. Aggregate push down ~ try to aggregate
> first when it is possible

What do you mean by "internal aggregate push down"? Partition-wise
aggregation? Aggregate/group by before join (something like [1])? IIUC,
what Jeevan proposes in this thread is to implement the aggregate push
down API that is specific to FDWs in postgres_fdw. Any other push down
work would need to use different APIs and would need to separately
proposed/discussed.

Thanks,
Amit

[1]
https://www.postgresql.org/message-id/CAKJS1f9kw95K2pnCKAoPmNw==7fgjSjC-82cy1RB+-x-Jz0QHA@mail.gmail.com