Return an RDD containing all pairs of elements with matching keys in
self and other.
Each pair of elements will be returned as a (k, (v1, v2)) tuple, where
(k, v1) is in self and (k, v2) is in other.
Performs a hash join across the cluster.
>>> x = sc.parallelize([("a", 1), ("b", 4)])
>>> y = sc.parallelize([("a", 2), ("a", 3)])
[('a', (1, 2)), ('a', (1, 3))]