CBO Predicate selectivity

Back to the basics.

I need any information on how CBO calculates [predicate] selectivity which is more precise than in the Note:68992.1

This note states that "c1 > :bind1 Default of 5%" which I doubt very much. At least it is not clear how distinct values/min-max values/datatype contribute to those 5% but the they do seem to contribute.

As a whole, CBO uses some heuristics (see Note:212809.1) which I need to tweak by manipulating statistics for one simple reason:

• I have a legacy query "where date between to_date(:b1) and to_date(b2)" => this query can not be modified.
• I know what CBO does not know: an index on date column must be used because selectivity of "date between to_date(:b1) and to_date(b2)" is high.

Thank you in advance,
Laimis
Fyrirvari/Disclaimer
http://www.landsbanki.is/disclaimer

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