Adaptive Oracle12c optimizer features eliminate the need for indexes?

Question

My database administrator believes that the new features of the Oracle12c optimizer mean that it no longer needs to add indexes to important columns. I hardly believe that this could be true. It only seems to improve how associations are performed based on historical statistics.

Answer 1

You are right, he completely misunderstood. You can read about Adaptive Query Optimization optimization in this white paper . This means that the optimizer can change the query execution plan during its operation. But if you do not index the columns that can benefit from them, the optimizer will not be able (adaptively or otherwise) to choose a plan that will benefit from these indices!