Re: Query optimizer 8.0.1 (and 8.0)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: pgsql(at)mohawksoft(dot)com
Cc: "Ron Mayer" <rm_pg(at)cheapcomplexdevices(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Query optimizer 8.0.1 (and 8.0)
Date: 2005-02-07 15:32:10
Message-ID: 27032.1107790330@sss.pgh.pa.us
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pgsql(at)mohawksoft(dot)com writes:
> On a very basic level, why bother sampling the whole table at all? Why not
> check one block and infer all information from that? Because we know that
> isn't enough data. In a table of 4.6 million rows, can you say with any
> mathmatical certainty that a sample of 100 points can be, in any way,
> representative?

This is a statistical argument, not a rhetorical one, and I'm not going
to bother answering handwaving. Show me some mathematical arguments for
a specific sampling rule and I'll listen.

regards, tom lane

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