What does '_._2' mean in spark

Question

This is a snippet of code in Spark/Scala:

 rdd.sortBy(_._2)

What does _._2 mean here?

See this post: https://stackoverflow.com/questions/29246440/apache-spark-what-is-map-2-shorthand-for — Rob212, Aug 23 '17 at 08:42

Krzysztof Atłasik · Answer 1 · 2017-08-23T08:53:10.780

5

In Scala _2 is shorthand for accessing second tuple element.

val myTuple = ("first", "second")
myTuple._1 // "first"
myTuple._2 // "second"

In your case all tuples in rdd will be sorted by second element. For example:

val tuples = Vector(("first", "b"),("second", "c"),("third", "a"))
tuples.sortBy(_._2) //Vector((third,a), (first,b), (second,c))

edited Aug 23 '17 at 08:53

answered Aug 23 '17 at 08:47

1 Answers1