Re: Vagaries of the CBO: Out-of-Range Predicates

From: Wolfgang Breitling <breitliw_at_centrexcc.com>
Date: Mon, 18 Dec 2006 05:34:55 -0700
Message-Id: <200612181235.kBICYuWj030465@mail64.megamailservers.com>

At 12:11 AM 12/18/2006, Anand Rao wrote:
>adding one more question,
>
>3) How does CBO calculate the density in cases of bind variables
>when the value is out of range?
>
>or is this a RTFM / RTFB ... ??

density is a "property" of the column and is roughly related to the probability of finding a particular value in the rows of the table. It is calculated when statistics are collected, not at parse time. density is in no way dependent on bind variables - or literals for that matter. You may be mistaking density with selectivity.

Regards

Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com

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Received on Mon Dec 18 2006 - 06:34:55 CST