spark pair RDD

1.含有“is”的行数
val lines = sc.textFile("file:///usr/spark/spark-1.0.0-bin-hadoop2/README.md")
lines.count
val isrdd = lines.filter(line => line.contains("is"))
isrdd.count

2.wordcount sort
val input = sc.textFile("file:///usr/spark/spark-1.0.0-bin-hadoop2/README.md")
input.take(10).foreach(println)

val words = input.flatMap(line => line.split(" "))
val count = words.map(word => (word,1)).reduceByKey(_+_).map(x=>(x._2, x._1)).sortByKey().map(x=>(x._2, x._1))
count.collect().foreach(println)

val input = sc.textFile("file:///usr/spark/spark-1.0.0-bin-hadoop2/README.md")
val count = input.flatMap(x => x.split(" ")).countByValue()

3.
val input = sc.parallelize(List((1,2),(3,4),(3,6)))
val r1 = input.groupByKey().collect()
val r1 = input.reduceByKey(_+_).collect()
val r1 = input.reduceByKey(_*_).collect()
val r1 = input.reduceByKey((x,y)=>(x+y)).collect()
val r1 = input.reduceByKey((x,y)=>(x-y)).collect()
val r1 = input.reduceByKey((x,y)=>(x max y)).collect()
input.keys.collect
input.values.collect
input.mapValues(x => x+1).collect

input.filter{case (key,value) => key > 2}.collect
input.filter{case (key,value) => value > 3}.collect

collect函数可以用来获取整个RDD中的数据，如果你的程序是在处理小规模的数据，并且在本地处理，可以使用collecte。如果数据单台机器放不下，不能使用。采用saveAsTextFile()放到HDFS。

当调用一个新的Action时，整个RDD都会从头开始计算，要避免这种低效行为，可以把中间结果持久化。