blue-sky blue-sky - 8 days ago 15x
Scala Question

How to print the contents of RDD?

I'm attempting to print the contents of a collection to the Spark console.

I have a type:

linesWithSessionId: org.apache.spark.rdd.RDD[String] = FilteredRDD[3]

And I use the command:

scala> => println(line))

But this is printed :

res1: org.apache.spark.rdd.RDD[Unit] = MappedRDD[4] at map at :19

How can I write the RDD to console or save it to disk so I can view its contents?


The map function is a transformation, which means that Spark will not actually evaluate your RDD until you run an action on it.

To print it, you can use foreach (which is an action):


To write it to disk you can use one of the saveAs... functions (still actions) from the RDD API