Joining two RDD[String] -Spark Scala

问题:

I have two RDDS :

rdd1 [String,String,String]: Name, Address, Zipcode
rdd2 [String,String,String]: Name, Address, Landmark 

I am trying to join these 2 RDDs using the function : rdd1.join(rdd2)
But I am getting an error :
error: value fullOuterJoin is not a member of org.apache.spark.rdd.RDD[String]

The join should join the RDD[String] and the output RDD should be something like :

rddOutput : Name,Address,Zipcode,Landmark

And I wanted to save these files as a JSON file in the end.

Can someone help me with the same ?

回答1:

As said in the comments, you have to convert your RDDs to PairRDDs before joining, which means that each RDD must be of type RDD[(key, value)]. Only then you can perform the join by the key. In your case, the key is composed by (Name, Address), so you you would have to do something like:

// First, we create the first PairRDD, with (name, address) as key and zipcode as value:
val pairRDD1 = rdd1.map { case (name, address, zipcode) => ((name, address), zipcode) }
// Then, we create the second PairRDD, with (name, address) as key and landmark as value:
val pairRDD2 = rdd2.map { case (name, address, landmark) => ((name, address), landmark) }

// Now we can join them. 
// The result will be an RDD of ((name, address), (zipcode, landmark)), so we can map to the desired format:
val joined = pairRDD1.fullOuterJoin(pairRDD2).map { 
  case ((name, address), (zipcode, landmark)) => (name, address, zipcode, landmark) 
}

More info about PairRDD functions in the Spark's Scala API documentation