how to skip empty rdd when join in spark

Question

I want to get 2 rdd from Cassandra,then join them.And I want to skip the empty value.

def extractPair(rdd: RDD[CassandraRow]) = {
    rdd.map((row: CassandraRow) => {

     val name = row.getName("name")
     if (name == "")
         None   //join wrong
     else
        (name, row.getUUID("object"))

    })
  }

  val rdd1 = extractPair(cassRdd1)
  val rdd2 = extractPair(cassRdd2)
  val joinRdd = rdd1.join(rdd2)  //"None" join wrong

use flatMap can fix this,but i want to know how to use map fix this

def extractPair(rdd: RDD[CassandraRow]) = {
        rdd.flatMap((row: CassandraRow) => {

         val name = row.getName("name")
         if (name == "")
             seq()
         else
            Seq((name, row.getUUID("object")))

        })
      }

Answer 1

This isn't possible with just a map. You would need to follow it up with a filter. But you would still be best to wrap the valid result in a Some. But, then you would still have it wrapped in a Some as a result...requiring a second map to unwrap it. So, realistically, your best option is something like this:

def extractPair(rdd: RDD[CassandraRow]) = {
  rdd.flatMap((row: CassandraRow) => {
    val name = row.getName("name")
    if (name == "") None
    else Some((name, row.getUUID("object")))
  })
}

Option is implicitly convertable to a flattenable type and conveys your methods message better.