A table function can be received at a database system and applied to one or more data sources. The table function can have one or more generic input operators associated with a source data type of the one or more data sources. One or more output operators associated with a return set of data of the table function can be determined at function call compile time from the values passed to one or more generic input operators. The determining of the one or more output parameters can be based on one or more rules specified in the table function definition. The one or more output operators for the table function can be generated at function call compile time.