Spark RDD sortByKey triggering a new job

[Spico Florin]

I have tested sortByKey method with the following code and I have observed
that is triggering a new job when is called. I could find this in the
neither in API nor in the code. Is this an indented behavior? For example,
the RDD zipWithIndex method API specifies that will trigger a new job. But
what about sortByKey?

val sc = new SparkContext(new SparkConf().setAppName("Spark Count"))
val l =sc.parallelize(List((5,'c'),(2,'d'),(1,'a'),(7,'e')), 3)

l.sortByKey()

Thanks for your answers.