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From: Simon Riggs <simon@2ndQuadrant.com>
To: Greg Stark <stark@enterprisedb.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: jd@commandprompt.com <jd@commandprompt.com>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: benchmarking the query planner
Date: Fri, 12 Dec 2008 18:18:02 +0000
Message-ID: <1229105882.8673.74.camel@ebony.2ndQuadrant> (raw)
In-Reply-To: <4136ffa0812121001x3fde1871t558fd8c58070b7d@mail.gmail.com>
References: <603c8f070812061019r5aca3aajeaa5493b11c5feff@mail.gmail.com>
	<1229039044.13078.193.camel@hp_dx2400_1>
	<4136ffa0812111823u645b6ec9wdca60b3da4b00499@mail.gmail.com>
	<1229072675.13078.196.camel@hp_dx2400_1>
	<603c8f070812120344m67ef2c1fs41806cfb4ff9e396@mail.gmail.com>
	<1229093975.13078.275.camel@ebony.2ndQuadrant>
	<87tz99s7bu.fsf@oxford.xeocode.com>
	<1229100057.8673.29.camel@ebony.2ndQuadrant>
	<87hc59s4qx.fsf@oxford.xeocode.com>
	<1229103209.8673.62.camel@ebony.2ndQuadrant>
	<4136ffa0812121001x3fde1871t558fd8c58070b7d@mail.gmail.com>


On Fri, 2008-12-12 at 18:01 +0000, Greg Stark wrote:

> I think you need to find two different formulas, one which represents
> a clustered table and one which represents randomly distributed data.
> Then you need a way to measure just how clustered the data is so you
> know how much weight to give each formula. Perhaps comparing the
> number of duplicates in whole-block samples versus overall random
> selections would give that measure.

Please read the Chaudhuri paper.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support

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