Spark算子：transformation之union、intersection、subtract

1、union：def union(other: RDD[T]): RDD[T]

该函数是不去重的合并两个RDD。

scala> var rdd1 = sc.makeRDD(1 to 2,1)
rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[45] at makeRDD at :21
 
scala> rdd1.collect
res42: Array[Int] = Array(1, 2)
 
scala> var rdd2 = sc.makeRDD(2 to 3,1)
rdd2: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[46] at makeRDD at :21
 
scala> rdd2.collect
res43: Array[Int] = Array(2, 3)
 //union合并
scala> rdd1.union(rdd2).collect
res44: Array[Int] = Array(1, 2, 2, 3)

2、intersection：

def intersection(other: RDD[T]): RDD[T]
def intersection(other: RDD[T], numPartitions: Int): RDD[T]
def intersection(other: RDD[T], partitioner: Partitioner)(implicit ord: Ordering[T] = null): RDD[T]

该函数是取两个RDD的交集，且去重。numPartitions表示分区数，partitioner表示分区函数。

scala> var rdd1 = sc.makeRDD(1 to 2,1)
rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[45] at makeRDD at :21
 
scala> rdd1.collect
res42: Array[Int] = Array(1, 2)
 
scala> var rdd2 = sc.makeRDD(2 to 3,1)
rdd2: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[46] at makeRDD at :21
 
scala> rdd2.collect
res43: Array[Int] = Array(2, 3)

 //intersection交集
scala> rdd1.intersection(rdd2).collect
res45: Array[Int] = Array(2)
 
scala> var rdd3 = rdd1.intersection(rdd2)
rdd3: org.apache.spark.rdd.RDD[Int] = MapPartitionsRDD[59] at intersection at :25
 
scala> rdd3.partitions.size
res46: Int = 1
 
scala> var rdd3 = rdd1.intersection(rdd2,2)
rdd3: org.apache.spark.rdd.RDD[Int] = MapPartitionsRDD[65] at intersection at :25
 
scala> rdd3.partitions.size
res47: Int = 2

3、subtract：

def subtract(other: RDD[T]): RDD[T]
def subtract(other: RDD[T], numPartitions: Int): RDD[T]
def subtract(other: RDD[T], partitioner: Partitioner)(implicit ord: Ordering[T] = null): RDD[T]

该函数是取两个RDD的差集，不去重。

scala> var rdd1 = sc.makeRDD(Seq(1,2,2,3))
rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[66] at makeRDD at :21
 
scala> rdd1.collect
res48: Array[Int] = Array(1, 2, 2, 3)
 
scala> var rdd2 = sc.makeRDD(3 to 4)
rdd2: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[67] at makeRDD at :21
 
scala> rdd2.collect
res49: Array[Int] = Array(3, 4)
 
scala> rdd1.subtract(rdd2).collect
res50: Array[Int] = Array(1, 2, 2)