25. A database system, comprising: a storage to store an indicator; and a controller including at least one processor to receive a database query containing a predicate expression that invokes a user-defined routine, and to receive a statement to set a value of the indicator, the controller to construct a first representation of the predicate expression in response to the indicator having a first value, and the controller to construct a second representation of the predicate expression in response to the indicator having a second value.
25. A database system, comprising: a storage to store an indicator; and a controller including at least one processor to receive a database query containing a predicate expression that invokes a user-defined routine, and to receive a statement to set a value of the indicator, the controller to construct a first representation of the predicate expression in response to the indicator having a first value, and the controller to construct a second representation of the predicate expression in response to the indicator having a second value. 35. The database system of claim 25 , wherein the controller is configured to further output a result produced by execution of the database query.