Oracle 10 optimizer from RULE to COST: why?

Question

Oracle decided to dismiss the rule-based optimizer from version 10g, leaving the cost-based one as the only choice.

I think that a rule-based optimizer has the unv

Answer 1

I think you should do rule based programming. Don't think about the situation, follow a list of inviolate rules, no matter what the situation, no matter what you think is the better way, if the rules say use a FOR LOOP in case X then you have to use a loop, even if you know if there will only be 1, loop from 1 to 1.

Stipulate:

Every query has a best plan.

Every query optimizer will determine that plan x% of the time.

The RBO had nowhere else to go, it's percent accuracy is lower than the CBO to be sure, but it was never going to get any better. It was limited like any rule based system.