When a resilient distributed dataset (RDD) is created from a text file or collection (or from another RDD), do we need to call “cache” or “persist” explicitly to store the RDD data into memory? Or is the RDD data stored in a distributed way in the memory by default?
val textFile = sc.textFile("/user/emp.txt")
As per my understanding, after the above step, textFile is a RDD and is available in all/some of the node’s memory.
If so, why do we need to call “cache” or “persist” on textFile RDD then?