Spark算子：RDD基本转换transform操作–union、intersection、subtract

╰+哭是因爲堅強的太久メ 2021-09-25 02:00 300阅读 0赞

Welcome to
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       /___/ .__/\_,_/_/ /_/\_\   version 2.4.5.online-JD2.4.5.16-202012212053
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    Using Scala version 2.11.12 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_121)
    Type in expressions to have them evaluated.
    Type :help for more information.

### union ###

def union(other: RDD\[T\]): RDD\[T\]

该函数比较简单，就是将两个RDD进行合并，**不去重**。

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)
     
    scala> rdd1.union(rdd2).collect
    res44: Array[Int] = Array(1, 2, 2, 3)

### 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\[T\]

该函数返回两个RDD的交集，并且**去重**。  
参数numPartitions指定返回的RDD的分区数。  
参数partitioner用于指定分区函数

scala>  var rdd1 = sc.makeRDD(Seq(1,2,2,3))
    rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[2] at makeRDD at <console>:24
    
    scala>  var rdd2 = sc.makeRDD(Seq(2,3,3,4,5))
    rdd2: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[3] at makeRDD at <console>:24
    
    scala> var rdd3 = rdd1.intersection(rdd2).collect;
    
    rdd3: Array[Int] = Array(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\[T\]

该函数类似于intersection，但返回在RDD中出现，并且不在otherRDD中出现的元素，**不去重**。  
参数含义同intersection

scala> var rdd1 = sc.makeRDD(Seq(1,1,1,2,2,3,6,6,7))
    rdd1: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[16] at makeRDD at <console>:24
    
    scala> var rdd3 = rdd1.subtract(rdd2).collect;
    
    rdd3: Array[Int] = Array(1, 1, 1, 6, 6, 7)

参考[http://lxw1234.com/archives/2015/07/345.htm][http_lxw1234.com_archives_2015_07_345.htm]

[http_lxw1234.com_archives_2015_07_345.htm]: http://lxw1234.com/archives/2015/07/345.htm