From: Richard Huxton <dev@archonet.com>
To: Martin Nickel <martin@portant.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Sequential scan on FK join
Date: Mon, 17 Oct 2005 18:45:38 +0100
Message-ID: <4353E342.2060708@archonet.com> (raw)
In-Reply-To: <pan.2005.10.17.13.07.53.915839@portant.com>
References: <pan.2005.10.12.20.40.22.703085@portant.com>
<4353648C.8040507@archonet.com>
<pan.2005.10.17.13.07.53.915839@portant.com>
Martin Nickel wrote:
> Subject: Re: Sequential scan on FK join
> From: Martin Nickel <martin@portant.com>
> Newsgroups: pgsql.performance
> Date: Wed, 12 Oct 2005 15:53:35 -0500
>
> Richard, here's the EXPLAIN ANALYZE. I see your point re: the 2.7M
> expected vs the 2 actual, but I've run ANALYZE on the lead table and it
> hasn't changed the plan. Suggestions?
>
> Hash Join (cost=62.13..2001702.55 rows=2711552 width=20)
> (actual time=40.659..244709.315 rows=2 125270 loops=1)
^^^
Hmm - is that not just a formatting gap there? Is it not 2,125,270 rows
matching which would suggest PG is getting it more right than wrong.
Try issuing "SET enable_seqscan=false" before running the explain
analyse - that will force the planner to use any indexes it can find and
should show us whether the index would help.
--
Richard Huxton
Archonet Ltd
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To: pgsql-performance@postgresql.org
Cc: dev@archonet.com, martin@portant.com
Subject: Re: Sequential scan on FK join
In-Reply-To: <4353E342.2060708@archonet.com>
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