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Re: Querying distinct values from a large table

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Gregory Stark <gsstark(at)mit(dot)edu>, Luke Lonergan <llonergan(at)greenplum(dot)com>, Chad Wagner <chad(dot)wagner(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Igor Lobanov <ilobanov(at)swsoft(dot)com>, Richard Huxton <dev(at)archonet(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Querying distinct values from a large table
Date: 2007-01-31 05:55:19
Message-ID: 16278.1170222919@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Gregory Stark wrote:
>> (Incidentally I'm not sure where 2-5x comes from. It's entirely dependant on
>> your data distribution. It's not hard to come up with distributions where it's
>> 1000x as fast and others where there's no speed difference.)

> So the figure is really "1-1000x"?  I bet this one is more impressive in
> PHB terms.

Luke has a bad habit of quoting numbers that are obviously derived from
narrow benchmarking scenarios as Universal Truths, rather than providing
the context they were derived in.  I wish he'd stop doing that...

			regards, tom lane

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