From: Josh Berkus <josh@agliodbs.com>
To: Bryan Murphy <bmurphy1976@gmail.com>
Cc: marcin mank <marcin.mank@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Help Me Understand Why I'm Getting a Bad Query Plan
Date: Wed, 25 Mar 2009 14:55:40 -0700
Message-ID: <49CAA85C.8080402@agliodbs.com> (raw)
In-Reply-To: <7fd310d10903242047t1a7b7daw1d61c3de7f20b7c6@mail.gmail.com>
References: <7fd310d10903231203r1bd37b8cn8baeadae83253f44@mail.gmail.com>
<7fd310d10903241521v1cbf5d7aueca653e03ed98649@mail.gmail.com>
<b1b9fac60903242004p5fe8b68fwd6f1ada767766b21@mail.gmail.com>
<7fd310d10903242047t1a7b7daw1d61c3de7f20b7c6@mail.gmail.com>
Bryan,
> One thing to keep in mind, due to a lapse in our judgement at the
> time, this itemexperiencelog table serves as both a current state
> table, and a log table. Therefore, it potentially has multiple
> redundant entries, but we typically only look at the most recent entry
> to figure out the state of the current item.
Oh, I see. It thinks that it'll need to pull 260,000 redundant rows in
order to get 1800 unique ones. Only it's wrong; you're only pulling
about 4000.
Try increasing some stats still further: itemexperiencelog.visitorid and
visitors.user_id both to 500.
--Josh
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To: pgsql-performance@postgresql.org
Cc: josh@agliodbs.com, bmurphy1976@gmail.com, marcin.mank@gmail.com
Subject: Re: Help Me Understand Why I'm Getting a Bad Query Plan
In-Reply-To: <49CAA85C.8080402@agliodbs.com>
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