Re: popular value is not popular in 10g?

This is specific to 10.1.0.5 and 10.2.0.1, which share many (maybe all) properties of histogram gathering. It appears that dbms_stats changed how it gathers histograms, e.g. it doesn't seem to use NTILE() any more or not as much. Your particular issue is fixed in 10.2.0.2.

At 07:13 PM 6/4/2006, jaromir nemec wrote:
>Hi List,
>
>while solving some funny problem concerning cardinality estimation with HB
>histogram I observed (Release 10.2.0.1.0, Windows) this behaviour that is
>neither logically explainable to me nor searchable on metalink.
>I’ll try to demonstrate it on a very simple example:
>If the column is populated as follows…
>[...]
>… a HB histogram is build and the value 3 is recognised as a popular
>value; SFSG.
>If the popular value is shifted to be the first value in the sorting
>order, like this …
>
>… HB histogram is build but suddenly the value 1 cease to be popular.
>Consider:
>
> SQL> EXPLAIN PLAN SET STATEMENT_ID = 'N1' into plan_table FOR
> 2 select * from h where h = 1;

Regards

Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com

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