Re: Stop Criteria for Sql Execution

as Jonathan pointed out already, the Oracle CBO *is* doing some pretty smart things in this area. However, you should always keep in mind that the optimizer is supposed to come back with a good plan as soon as possible; if parsing takes excessive time, the quality of the execution plan becomes less important or even irrelevant, in general.

Examining a complicated WHERE clause to see tautologies and/or contradictions is not as straighforward as it sometimes seems, given the fact that we have to deal with three-valued logic.

cheers,
Lex.

> Why does Oracle have to execute the sql and scan data in a table for a
> sql like this:
>
> Select * from table
> Where column1 is null and column1=3D10
>
> Or=20
>
> Select * from table
> Where column1=3D10 and column1=3D20
>
> All the research money going to optimize the optimizer, and still can't
> take care of simple stuff like this.
>
> Am I missing something?
>
> I will probably start searching for smarter databases :)
>
> Waleed
> --
> http://www.freelists.org/webpage/oracle-l
>

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