Hi,
When I try to implement https://issues.apache.org/jira/browse/FLINK-5498
via "dataset.coGroup(another dataset)" with a generated
CoGroupFunction.(CoGroupFunction
interface: public void coGroup(Iterable<IN1> first, Iterable<IN2> second,
Collector<O> out)
I couldn't get the right results, then I saw the backend Iterator did
not supply a new instance when invoked the "Iterable.iterator()" after
debugging.
(see org.apache.flink.api.common.operators.util.ListKeyGroupedIterator,
it differs from usual iterable collections in java which will implement
the iterator() method that supply a new iterator instance for the
collection. And this is not mentioned either in comments or document.)
IMO, iterable collections' new iterator instance requirements probably
useful for other cases, so is it necessary to add this feature?
Greatful if someone can tell me the motivation that ListKeyGroupedIterator
didn't supply a new iterator instance.
What do you think?
Best, Lincoln
