Union-Method does not function

[Alexander Sirotin]

Hello everybody,

I am reading a text-file and like to outer-join it with another 
text-file. Because I do not know, how to call an outer-join throw Flink, 
I am adding a dummy-row "-1" via union to one of these Dataset:

        DataSet<Tuple3<String, Integer, Integer>> myNull = env
                .fromElements(new Tuple3<String, Integer, Integer>("-1",
                        new Integer(-1), new Integer(-1)));

        names = names.union(myNull);

But if I look to the results, I never can see this value or the values 
from the other datasets, who should be joined with it.

Thank you very much. I hope someone knows how I can solve this problem.

Best regards,
Alex