Very strange behaviour of groupBy() -> sort() -> first()

[Felix Neutatz]

Hi,

my use case is the following:

I have a Tuple2<String,Long>. I want to group by the String and sum up the
Long values accordingly. This works fine with these lines:

DataSet<Lineitem> lineitems = getLineitemDataSet(env);
lineitems.project(new int []{3,0}).groupBy(0).aggregate(Aggregations.SUM,
1);

After the aggregation I want to print the 10 groups with the highest sum,
like:

string1, 100L
string2, 50L
string3, 1L

I tried that:

lineitems.project(new int []{3,0}).groupBy(0).aggregate(Aggregations.SUM,
1).groupBy(0).sortGroup(1, Order.DESCENDING).first(3).print();

But instead of 3 records, I get a lot more.

Can see my error?

Best regards,

Felix