Hi Robert, thanks, I will post my future questions to that list.
Regarding your question: When using the Tuples, you don't need to specify a > keySelector. It is sufficient to specify the ID(s) of the keys: > http://stratosphere-javadocs.github.io/eu/stratosphere/api/java/DataSet.html#groupBy(int.. > .) > So you should be able to do a ".groupBy(0,3,4)" > > Actually my question is about the situation when I don't have tuples. Assume I have a DataSet<UserData> ds and I want to invoke ds.groupBy(/* grouping by <userId, sessionId, dayOfTheYear> */), the ideal choice would be to return a comparable tuple from the KeySelector. On the side note, would it be possible to generate the clone method for the tuples? Yesterday I was copying a Tuple13 in a groupReduce function by hand and it was a pretty long line of code :) Thanks, Vyacheslav
