Posted by
Fabian Hueske on
Jun 18, 2014; 12:46pm
URL: http://deprecated-apache-flink-mailing-list-archive.368.s1.nabble.com/Fwd-stratosphere-users-FlatJoin-implementation-tp394p424.html
What do you mean by "collect the left side" and "union"? If you want to
collect all elements of the left/right side grouped by key, you should use
CoGroup. For union you use the Union transformation. If you want to "union"
the fields of the inputs you use the projectJoin.
The question is about the output of a join function. Right know, it must
return exactly one element. A FlatJoin function would allow to return 0, 1,
or n elements. A ProjectJoin or DefaultJoin and a following FlatMap
realizes the same functionality, but is not as nice to use as a FlatJoin.
2014-06-18 14:38 GMT+02:00 Ufuk Celebi <
[hidden email]>:
>
> On 18 Jun 2014, at 14:31, Fabian Hueske <
[hidden email]> wrote:
>
> > Why not?
> > You do
> >
> >
> data1.join(data2).where(0).equalTo(0).projectFirst(0,1).projectSecond(1).types(Long.class,
> > Long.class, Long.class).flatMap(new MyFM())
>
> What if I want the join to collect the left side, right side and union?
> But I'm not sure how realistic this use case is and if it is what Asterios
> had in mind?