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Re: Unexpected query plan results

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Anne Rosset <arosset(at)collab(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Unexpected query plan results
Date: 2009-05-29 21:32:54
Message-ID: 603c8f070905291432o4d0ff1fdo699a21a7092477f5@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Thu, May 28, 2009 at 6:46 PM, Anne Rosset <arosset(at)collab(dot)net> wrote:
>                                                  ->  Index Scan using
> item_pk on item  (cost=0.00..176865.31 rows=97498 width=88) (actual
> time=117.304..2405.060 rows=71 loops=1)
>                                                        Filter: ((NOT
> is_deleted) AND ((folder_id)::text = 'tracker3641'::text))

The fact that the estimated row count differs from the actual row
count by a factor of more than 1000 is likely the root cause of your
problem here.  You probably want to figure out why that's happening.
How many rows are in that table and what value are you using for
default_statistics_target?

...Robert

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