Extra functions available on RDDs of (key, value) pairs where the key is sortable through
an implicit conversion. Import spark.SparkContext._ at the top of your program to use these
functions. They will work with any key type that has a scala.math.Ordered implementation.
Sort the RDD by key, so that each partition contains a sorted range of the elements.
Sort the RDD by key, so that each partition contains a sorted range of the elements. Calling
collect or save on the resulting RDD will return or output an ordered list of records
(in the save case, they will be written to multiple part-X files in the filesystem, in
order of the keys).