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
--
http://www.freelists.org/webpage/oracle-l