Re: Combining Aggregates

From: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Amit Kapila <amit(dot)kapila(at)enterprisedb(dot)com>
Subject: Re: Combining Aggregates
Date: 2015-12-03 05:01:53
Message-ID: CAKJS1f9wfPKSYt8CG=T271xbyMZjRzWQBjEixiqRF-oLH_u-Zw@mail.gmail.com
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On 27 July 2015 at 04:58, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:

>
> This patch seems sane to me, as far as it goes. However, there's no
> planner or executor code to use the aggregate combining for anything. I'm
> not a big fan of dead code, I'd really like to see something to use this.
>

I've attached an updated version of the patch. The main change from last
time is that I've added executor support and exposed this to the planner
via two new parameters in make_agg().

I've also added EXPLAIN support, this will display "Partial
[Hash|Group]Aggregate" for cases where the final function won't be called
and displays "Finalize [Hash|Group]Aggregate" when combining states and
finalizing aggregates.

This patch is currently intended for foundation work for parallel
aggregation.

--
David Rowley http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Training & Services

Attachment Content-Type Size
combine_aggregate_state_6ea1aad_2015-12-03.patch application/octet-stream 68.9 KB

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