在一个文件中对spark RDD进行排序和排名

SparkRDD函数（所谓的转换）groupByKey flatMap和ScalaList函数一样sorted应该有助于实现它。

val rdd = spark.sparkContext.parallelize(
Seq(("maths",60),

  ("english",65), 
  ("english",77), 
  ("maths",23), 
  ("maths",50)))

val result = rdd.groupByKey().flatMap(group => {

group._2.toList
.sorted.toList // sort marks
.zipWithIndex // add the position/rank
.map {

case(marks, index) => (group._1, marks, index + 1)

}
})

result.collect

// Array((english,65,1), (english,77,2), (maths,23,1), (maths,50,2), (maths,60,3))