From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tony Capobianco <tcapobianco@prospectiv.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Oracle v. Postgres 9.0 query performance
Date: Wed, 08 Jun 2011 11:33:05 -0400
Message-ID: <10260.1307547185@sss.pgh.pa.us> (raw)
In-Reply-To: <1307545892.1990.23.camel@tony1.localdomain>
References: <1307545892.1990.23.camel@tony1.localdomain>
Tony Capobianco <tcapobianco@prospectiv.com> writes:
> pg_dw=# explain CREATE TABLE ecr_opens with (FILLFACTOR=100)
> pg_dw-# as
> pg_dw-# select o.emailcampaignid, count(memberid) opencnt
> pg_dw-# from openactivity o,ecr_sents s
> pg_dw-# where s.emailcampaignid = o.emailcampaignid
> pg_dw-# group by o.emailcampaignid;
> QUERY
> PLAN
> -------------------------------------------------------------------------------------------------------------
> GroupAggregate (cost=0.00..1788988.05 rows=9939 width=12)
> -> Nested Loop (cost=0.00..1742467.24 rows=9279316 width=12)
> -> Index Scan using ecr_sents_ecid_idx on ecr_sents s
> (cost=0.00..38.59 rows=479 width=4)
> -> Index Scan using openact_emcamp_idx on openactivity o
> (cost=0.00..3395.49 rows=19372 width=12)
> Index Cond: (o.emailcampaignid = s.emailcampaignid)
> (5 rows)
> Should this query be hashing the smaller table on Postgres rather than
> using nested loops?
Yeah, seems like it. Just for testing purposes, do "set enable_nestloop
= 0" and see what plan you get then.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, tcapobianco@prospectiv.com
Subject: Re: Oracle v. Postgres 9.0 query performance
In-Reply-To: <10260.1307547185@sss.pgh.pa.us>
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