We recently received advanced Oracle training from an Oracle consultant
who's been working in the industry for decades.
He claimed that Rules based queries almost always outperform Cost based
queries and he advised us to turn off the costing functions.
To optimize query performance he recommended using EXPLAIN PLAN. In order
to take advantage of EXPLAIN PLAN you have to know which basic functions
allow for greater performance, and how reordering or changing your query
will change the basic functions that Oracle chooses to implement your
query. He was able to distill his years of experience into a basic list
of do's and dont's.