Spark, scala group by example

our source dataset resides here : http://stat-computing.org/dataexpo/2009/the-data.html

and this is how I worked out to parse the csv file and reduce by airport (column 17)

[root@nodo1 spark]# ./bin/spark-shell --master spark://nodo1:7077
scala> import au.com.bytecode.opencsv.CSVParser
import au.com.bytecode.opencsv.CSVParser

scala> import org.apache.spark.rdd.RDD
import org.apache.spark.rdd.RDD

scala> val myfile = sc.textFile("hdfs://nodo1/claudio/2008.csv").cache()
15/02/04 16:37:35 INFO storage.MemoryStore: ensureFreeSpace(139132) called with curMem=0, maxMem=311387750
15/02/04 16:37:35 INFO storage.MemoryStore: Block broadcast_0 stored as values to memory (estimated size 135.9 KB, free 296.8 MB)
myfile: org.apache.spark.rdd.RDD[String] = MappedRDD[1] at textFile at <console>:14

scala> myfile.mapPartitions(lines => {
         val parser = new CSVParser(',')
         lines.map(line => {
           parser.parseLine(line).mkString(",")
         })
       }).take(5).foreach(println)

scala> def dropHeader(data: RDD[String]): RDD[String] = {
         data.mapPartitionsWithIndex((idx, lines) => {
           if (idx == 0) {
             lines.drop(1)
           }
           lines
         })
       }

scala> val withoutHeader: RDD[String] = dropHeader(myfile)
scala> withoutHeader.mapPartitions(lines => {
         val parser = new CSVParser(',')
         lines.map(line => {
           parser.parseLine(line).mkString(",")
         })
       }).take(5).foreach(println)

scala> withoutHeader.mapPartitions(lines => {
         val parser=new CSVParser(',')
         lines.map(line => {
           val columns = parser.parseLine(line)
           Array(columns(16)).mkString(",")
         })
       }).countByValue().toList.sortBy(-_._2).foreach(println)

(ATL,414513)
(ORD,350380)
(DFW,281281)
(DEN,241443)
(LAX,215608)
(PHX,199408)
(IAH,185172)
(LAS,172876)
(DTW,161989)

(SFO,140587)