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
