Re: CBO question ?

> CHOOSE 'IS' CBO
> pls read at <http://tahiti.oracle.com/> http://tahiti.oracle.com, perf
> tuning guide.

?

Oracle 9i, Database Reference
Release 2 (9.2)

<quote>
choose
The optimizer chooses between a cost-based approach and a rule-based approach based on whether statistics are available. If the data dictionary contains statistics for at least one of the accessed tables,
then the optimizer uses a cost-based approach and optimizes with a goal of best
throughput. If the data dictionary contains only some statistics, then the cost-based approach is used, and the optimizer must guess the statistics for the
subjects without any statistics. This can result in sub-optimal execution plans. If
the data dictionary contains no statistics for any of the accessed tables, then the
optimizer uses a rule-based approach.
</quote>

Regards,
Dimitre

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