Hi there, I read the code a bit, though I am not sure if I get it right. It appears to me that when memory buffer of mapper is full, it spills and gets sorted by partition id and by keys. Then, if there is a combiner defined, it will work on each partition. However, it seems that the outputs of a combiner are put in the same input partition, which means that the keys emit by a combiner have to be in the same partition as the inputs to it. Is this the case?
Best, -Kevin
