31. The system of claim 23 , wherein said optimizer module evaluates execution costs of a candidate plan segment to be added to an access plan being constructed.
31. The system of claim 23 , wherein said optimizer module evaluates execution costs of a candidate plan segment to be added to an access plan being constructed. 33. The system of claim 31 , wherein said optimizer module evaluates execution costs of partial access plans being constructed and prunes candidate plan segments having unfavorable execution costs.