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Re: Bad n_distinct estimation; hacks suggested?

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: pgsql-perform <pgsql-performance(at)postgresql(dot)org>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: Bad n_distinct estimation; hacks suggested?
Date: 2005-04-23 23:53:16
Message-ID: 200504231653.16317.josh@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
People,

> Can someone whose math is more recent than calculus in 1989 take a look at
> that paper, and look at the formula toward the bottom of page 10, and see
> if we are correctly interpreting it?    I'm particularly confused as to
> what "q" and "d-sub-n" represent.  Thanks!

Actually, I managed to solve for these and it appears we are using the formula 
correctly.  It's just a bad formula.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

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