Chesnay is right. What you want is a non-grouped sort/first, which would need to be added...
Stephan Am 21.01.2015 11:25 schrieb "Chesnay Schepler" < chesnay.schep...@fu-berlin.de>: > If i remember correctly first() returns the first n values for every > group. the javadocs actually don't make this behaviour very clear. > > On 21.01.2015 19:18, Felix Neutatz wrote: > >> 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 >> >> >