Re: Compute statisics

On Tuesday 05 June 2001 01:20, Connor McDonald wrote:
> Sounds like nonsense to me...If you have "half"
> statistics, then the optimizer is going to use
> defaults for the others,

Conner,

Are you sure about that?

>From the Optimizer chapter in the tuning manual:

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 no statistics for any of the accessed tables, then the optimizer uses a rule-based approach. This is the default value for the parameter.

...

If the optimizer uses the cost-based approach for a SQL statement, and if some tables accessed by the statement have no statistics, then the optimizer uses internal information (such as the number of data blocks allocated to these tables) to estimate other statistics for these tables.

That coupled with the fact that when viewing the plan table you can see the CBO's use of the statistic would make me think otherwise.

Is there some documentation that I missed that supports the CBO using defaults for analyzed tables when some of them are _not_ analyzed?

Or did I just misunderstand your post?

Jared

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