Performs an inner join between two RDDs, followed by a groupBy on the right object.
The 'left' side of the join
The 'right' side of the join
An RDD of pairs (Iterable[x], y), where the Iterable[x] is from baseRDD, y is from joinedRDD, and all values in the Iterable[x] are aligned at regions that overlap the region corresponding to y. If the iterable is empty, the key-value pair is filtered out.