Your observation is correct, the combine code will not execute if you disable the reduce phase, i.e. set numbers of reducers to 0.
Actually, the combine code might not be executed with a reduce phase, or it might be executed more than once on the map output. It’s the framework’s decision, so don’t put anything into the combine code you expect to run. Kai > Am 20.12.2014 um 17:53 schrieb Todd <[email protected]>: > > Hi, Hadoopers, > It looks to me that when I provide the combiner but doesn't provide the > reducer,the combiner doesn't take effect or combiner doesn't get run at all. > I don't understand here because the combiner is running on the Mapper node, > so could some one please explain the behavior of Combiner?Thanks. Kai Voigt Am Germaniahafen 1 [email protected] 24143 Kiel +49 160 96683050 Germany @KaiVoigt
