Thanks, @Fabian, your workaround works :)
But I think this feature is really missing. Shall we add this functionality
natively or via the proposed lib package?
2015-01-21 20:38 GMT+01:00 Fabian Hueske <fhue...@gmail.com>:
> Chesnay is right.
> Right now, it is not possible to do want you want in a straightforward way
> because Flink does not support to fully sort a data set (there are several
> related issues in JIRA).
>
> A workaround would be to attach a constant value to each tuple, group on
> that (all tuples are sent to the same group), sort that group, and apply
> the first operator.
>
> 2015-01-21 20:22 GMT+01:00 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
> >>
> >>
> >
>
