如何在值上膨胀对RDD？

每当充气"flatMap"时非常有用

val x = List(("cat", List(2, 4)), ("dog", List(6, 5, 4)))
val rdd = sc.parallelize(x)
val y = rdd.flatMap{ case(x, y) => y.map((x, _))}
y.collect().foreach(println)

产量

(cat,2)
(cat,4)
(dog,6)
(dog,5)
(dog,4)