1. A method of optimizing the execution of a database statement, comprising: receiving a database statement comprising a predicate; submitting a lower bounding value to an optimizer function, said lower bounding value defining a lower boundary of a range of values for said predicate; submitting an upper bounding value to said optimizer function, said upper bounding value defining an upper boundary of said range of values for said predicate; and using said optimizer function to estimate costs of an execution plan for said database statement.