> Yes. We've talked about adding various checks, but I don't think anyone has
> added them. We obviously have the input key and one option would be to
> ignore the output key.
>> Since a Combiner is simply a Reducer with no other constraints,
> That isn't true. Combiners are required to be:
When I meant 'Reducer with no other constraints' I meant
Job.setCombinerClass takes a Class<? extends Reducer>, not a Combiner
class which enforces stricter constraints.
Thanks for listing the 5 requirements, if you don't mind I'll add them
to the Hadoop MapReducer Poster.