A method and system for optimizing the execution of database statements are described. An aspect is directed to the generation of an execution plan for a database statement, wherein the database statement contains a predicate having one or more arguments whose values are not known at the time the execution plan is generated (e.g., at compile time). A feature of this aspect involves passing a description of the argument(s) to the optimizer. An example of such a description includes the argument type of the predicate argument.