Using Spark transformations to defer computations to a later time

Let's first understand Spark DAG creation. We will be executing DAG by issuing the action and also deferring the decision about starting the job until the last possible moment to check what this possibility gives us.

Let's have a look at the code we will be using in this section.

First, we need to initialize Spark. Every test we carry out will be the same. We need to initialize it before we start using it, as shown in the following example:

class DeferComputations extends FunSuite {
val spark: SparkContext = SparkSession.builder().master("local[2]").getOrCreate().sparkContext

Then, we will have the actual test. Here, test is called should defer computation. It is simple but shows a very powerful abstraction of Spark. We start by creating an rdd of InputRecord, as shown in the following example...