Re: Rule-based vs Cost-based Optimizer?

I habe been in the same dileema of using Cost-based or Rule-based optimization. The basic difference is that cost-based uses Sort-merge, and if your sort area is pretty large(depending upon the result set returned by the query) cost-based consistently outperforms Rule-based. However, the approach I have taken is to invoke cost-based for a query instead of applying it to the whole of database. I always do a retrieve on bath Rule and Cost based and whichever is better, use that. Also, if your queries join 4 or more tables, be very cautious in using cost based. Received on Tue Apr 11 1995 - 00:00:00 CEST