Re: performance problem with LIMIT (order BY in DESC order). Wrong index used?

From: Dieter Rehbein <dieter(dot)rehbein(at)skiline(dot)cc>
To: Claudio Freire <klaussfreire(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: performance problem with LIMIT (order BY in DESC order). Wrong index used?
Date: 2011-04-12 09:36:23
Message-ID: 93F9FA07-1BFF-4052-98FA-56FFF9D5E39D@skiline.cc
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thank's a lot guys, I will try that out.

regards
Dieter

Am 12.04.2011 um 11:07 schrieb Claudio Freire:

On Tue, Apr 12, 2011 at 10:59 AM, Dieter Rehbein
<dieter(dot)rehbein(at)skiline(dot)cc> wrote:
> I just executed a VACUUM ANALYZE and now everything performs well. hm, strange.

That probably means you need more statistics - try increasing the
newsfeed's statistics target count.

ALTER TABLE newsfeed_item ALTER COLUMN newsfeed SET STATISTICS <n>;

Try different <n> numbers, you can crank it up to 4000 or perhaps more
in 9.0, but you should start lower I guess.

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