Grouping by a tuple

[Vyacheslav Zholudev]

Hi,

Being used to the Hive grouping like "GROUP BY userId, productId, year" I'm wondering what's the best way to do it in Stratosphere? The groupBy's KeySelector implies that a Comparable object is returned, however, the obvious choice like TupleN is not comparable. In primitive cases I would prefer to avoid introducing comparable extra entities for grouping tuples of "primitive" types. Would it make sense to introduce "ComparableTupleN<T1 extends Comparable<? extends T1>, ..., Tn extends Comparable<? extends Tn>>"?

Or am I missing the obvious way in a Stratosphere way?

Thanks,
Vyacheslav

[Robert Metzger]

Hi Slava,

I'm forwarding your message to our new mailing list at Apache: d...@flink.incubator.apache.org

You can subscribe to the list by sending an (empty) email to: dev-su...@flink.incubator.apache.org.

We are planning to shut down the stratosphere-dev@googlegroups soon.

Regarding your question: When using the Tuples, you don't need to specify a keySelector. It is sufficient to specify the ID(s) of the keys: http://stratosphere-javadocs.github.io/eu/stratosphere/api/java/DataSet.html#groupBy(int...)

So you should be able to do a ".groupBy(0,3,4)"

Robert

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