Questions 2 and 3 can be answered relatively easily: Remember, the output of the combiner is going to be consumed by the reducer. So the output key/vlaue classes of the combiner have to align with the input key/vlaue classes of the reducer.
On Mon, May 23, 2011 at 11:32 AM, Mike Spreitzer <[email protected]>wrote: > In general, the Java interfaces say that one invocation of a combiner > (technically, a Class<? *extends* Reducer>) can output multiple > (key,value) pairs. So: > > What happens if one invocation of a combiner outputs more than one value? > > What happens if an output key is different from the input key? > > What happens if an output value is of a different class than the class of > the input values? > > Thanks, > Mike Spreitzer >
