> 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.
ok. > >> 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.
