Assume say JavaWord count
I call the equivalent of a Mapper
JavaPairRDD<String, Integer> ones = words.mapToPair(,,,
Now right here I want to guarantee that each word starting with a
particular letter is processed in a specific partition - (Don't tell me
this is a dumb idea - I know that but in a Hadoop code a custom partitioner
is often important and I don't want to explain the real case)
I have no idea how ones would implement such partitioning here or what code
would look like assuming mapToPartition was used
JavaPairRDD<String, Integer> counts = ones.reduceByKey(...
