private FunctionInfo registerGenericUDTF(String functionName, FunctionType functionType,
      Class<? extends GenericUDTF> genericUDTFClass, FunctionResource... resources) {
    validateClass(genericUDTFClass, GenericUDTF.class);
    validateDescription(genericUDTFClass);
    FunctionInfo fI = new FunctionInfo(functionType, functionName,
        ReflectionUtil.newInstance(genericUDTFClass, null), resources);
    addFunction(functionName, fI);
    return fI;
  }
Registers the UDF class as a built-in function; used for dynamically created UDFs, like
GenericUDFOP*Minus/Plus.
ql/src/java/org/apache/hadoop/hive/ql/exec/Registry.java