Re: multi-column indexes, statistics and selectivity

From: Robert Klemme <>
Date: Sun, 06 Dec 2009 13:33:06 +0100
Message-ID: <>

On 05.12.2009 22:35, Mladen Gogala wrote:
> On Sat, 05 Dec 2009 14:18:38 +0100, Robert Klemme wrote:
>> Are there cases where it makes sense to use a FBI to get "multi column"
>> histogram information?

> Hmmm, let me quote from the 11g book: if the columns are related in the
> way that breaks the 3rd normal form, such statistics would make sense.
> The famous example by Jonatan was about zodiac signs and months of birth.
> The 10g CBO would produce an incorrect estimate for the number of people
> with the sign of Capricorn born in June. There are, of course, none, but
> you can't know that without a multi-column histogram.

That makes a lot of sense! Thank you, Mladen!

Kind regards


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Received on Sun Dec 06 2009 - 06:33:06 CST

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