are you sure it can be run in the reduce task? if it does it's still before the reducer is called though... so the flow of your data will still be: data -> mapper(s) -> optional reducer(s) -> reducer(s) -> output_data
On Fri, Dec 4, 2009 at 1:42 PM, Owen O'Malley <[email protected]> wrote: > On Fri, Dec 4, 2009 at 12:32 PM, Raymond Jennings III <[email protected] >> wrote: > >> Does the combiner run once per data node or one per map task? (That it can >> run multiple times on the same data node after each map task.) Thanks. >> > > The combiner can run 0, 1, or many times on each data value. It can run in > both the map task and reduce task. > > -- Owen >
