| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Push down Aggregates below joins |
| Date: | 2018-06-20 21:05:38 |
| Message-ID: | 232cda0a-00b1-c375-b595-2bb0460b43a0@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 06/20/2018 10:12 PM, Heikki Linnakangas wrote:
> Currently, the planner always first decides the scan/join order, and
> adds Group/Agg nodes on top of the joins. Sometimes it would be legal,
> and beneficial, to perform the aggregation below a join. I've been
> hacking on a patch to allow that.
>
There was a patch [1] from Antonin Houska aiming to achieve something
similar. IIRC it aimed to push the aggregate down in more cases,
leveraging the partial aggregation stuff. I suppose your patch only aims
to do the pushdown when the two-phase aggregation is not needed?
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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