Re: Query with large number of joins

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Marco Di Cesare <Marco(dot)DiCesare(at)pointclickcare(dot)com>
Cc: Merlin Moncure <mmoncure(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Query with large number of joins
Date: 2014-10-21 16:50:32
Message-ID: 6155.1413910232@sss.pgh.pa.us
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Marco Di Cesare <Marco(dot)DiCesare(at)pointclickcare(dot)com> writes:
> COUNT(DISTINCT "foxtrot_india"."bravo_romeo")

Ah. That explains why the planner doesn't want to use a hash aggregation
step --- DISTINCT aggregates aren't supported with those.

regards, tom lane

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