@Override
    public Object evaluate(ExecutionContext context) throws FunctionDomainException,
        TypeMismatchException, NameResolutionException, QueryInvocationTargetException {
      throw new UnsupportedOperationException("Method execution not expected");
    }
@return null if null is on the stack
geode-core/src/main/java/org/apache/geode/cache/query/internal/QCompiler.java