Re: selecting a column according to a minimum

Mikito Harakiri wrote:

> As far as optimizer is concerned, execution plan tells you only one
> part of the story: physical optimizer. Query transformation/rewrite is
> arguably much more sophisticated part and is not reflected an plan
> table or trace file. BTW, does DB2 exposes the decision tree of
> transformations somehow?

No, not for regular users, but presumably the migration of, say, a group by through a union, the pruning of a branch in a union, inline view splitting/unification, predicate elimination due to theorem proving etc are all things that can be deduced from the final plan (at least in DB2 for LUW).
DB2 however prints the "optimized SQL" which allows for better correlation with the plan.

Cheers
Serge Received on Wed Oct 20 2004 - 13:17:47 CDT