spark算子

简单来说，Spark 算子大致可以分为以下两类:

Transformation 变换/转换算子：这种变换并不触发提交作业，完成作业中间过程处理。
Transformation 操作是延迟计算的，也就是说从一个RDD 转换生成另一个 RDD 的转换操作不是马上执行，需要等到有 Action 操作的时候才会真正触发运算。
Action 行动算子：这类算子会触发 SparkContext 提交 Job 作业。
Action 算子会触发 Spark 提交作业（Job），并将数据输出 Spark系统。

从小方向来说，Spark 算子大致可以分为以下三类:

Value数据类型的Transformation算子，这种变换并不触发提交作业，针对处理的数据项是Value型的数据。
Key-Value数据类型的Transfromation算子，这种变换并不触发提交作业，针对处理的数据项是Key-Value型的数据对。
Action算子，这类算子会触发SparkContext提交Job作业

http://spark.apache.org/docs/1.6.3/programming-guide.html 官方参考文档

spark算子大致上可分三大类算子：

　　1、Value数据类型的Transformation算子，这种变换不触发提交作业，针对处理的数据项是Value型的数据。

　　2、Key-Value数据类型的Transformation算子，这种变换不触发提交作业，针对处理的数据项是Key-Value型的数据。

　　3、Action算子，这类算子会触发SparkContext提交作业。

一、Value型Transformation算子

1）map

map()：将原来 RDD 的每个数据项通过 map 中的用户自定义函数 f 映射转变为一个新的元素。

val a = sc.parallelize(List("dog", "salmon", "salmon", "rat", "elephant"), 3)

val b = a.map(_.length)

val c = a.zip(b)

c.collect

res0: Array[(String, Int)] = Array((dog,3), (salmon,6), (salmon,6), (rat,3), (elephant,8))

2）flatMap

flatMap(function) ：并将生成的 RDD 的每个集合中的元素合并为一个集合

val a = sc.parallelize(1 to 10, 5)

a.flatMap(1 to _).collect

res47: Array[Int] = Array(1, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

sc.parallelize(List(1, 2, 3), 2).flatMap(x => List(x, x, x)).collect

res85: Array[Int] = Array(1, 1, 1, 2, 2, 2, 3, 3, 3)

3）mapPartiions

mapPartitions(function) ：map()的输入函数是应用于RDD中每个元素，而mapPartitions()的输入函数是应用于每个分区。

val x = sc.parallelize(1 to 10, 3)

x.flatMap(List.fill(scala.util.Random.nextInt(10))(_)).collect

res1: Array[Int] = Array(1, 2, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10)

4）glom（形成一个Array数组）

val a = sc.parallelize(1 to 100, 3)

a.glom.collect

res8: Array[Array[Int]] = Array(Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33), Array(34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66), Array(67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100))

5）union

val a = sc.parallelize(1 to 3, 1)

val b = sc.parallelize(5 to 7, 1)

(a ++ b).collect

res0: Array[Int] = Array(1, 2, 3, 5, 6, 7)

6）cartesian（笛卡尔操作）

val x = sc.parallelize(List(1,2,3,4,5))

val y = sc.parallelize(List(6,7,8,9,10))

x.cartesian(y).collect

res0: Array[(Int, Int)] = Array((1,6), (1,7), (1,8), (1,9), (1,10), (2,6), (2,7), (2,8), (2,9), (2,10), (3,6), (3,7), (3,8), (3,9), (3,10), (4,6), (5,6), (4,7), (5,7), (4,8), (5,8), (4,9), (4,10), (5,9), (5,10))

7）groupBy（生成相应的key，相同的放在一起）

val a = sc.parallelize(1 to 9, 3)

a.groupBy(x => { if (x % 2 == 0) "even" else "odd" }).collect

res42: Array[(String, Seq[Int])] = Array((even,ArrayBuffer(2, 4, 6, 8)), (odd,ArrayBuffer(1, 3, 5, 7, 9)))

8）filter

val a = sc.parallelize(1 to 10, 3)

val b = a.filter(_ % 2 == 0)

b.collect

res3: Array[Int] = Array(2, 4, 6, 8, 10)

9）distinct（去重）

val c = sc.parallelize(List("Gnu", "Cat", "Rat", "Dog", "Gnu", "Rat"), 2)

c.distinct.collect

res6: Array[String] = Array(Dog, Gnu, Cat, Rat)

10）subtract（去掉含有重复的项）

val a = sc.parallelize(1 to 9, 3)

val b = sc.parallelize(1 to 3, 3)

val c = a.subtract(b)

c.collect

res3: Array[Int] = Array(6, 9, 4, 7, 5, 8)

11）sample

val a = sc.parallelize(1 to 10000, 3)

a.sample(false, 0.1, 0).count

res24: Long = 960

12）takesample

val x = sc.parallelize(1 to 1000, 3)

x.takeSample(true, 100, 1)

res3: Array[Int] = Array(339, 718, 810, 105, 71, 268, 333, 360, 341, 300, 68, 848, 431, 449, 773, 172, 802, 339, 431, 285, 937, 301, 167, 69, 330, 864, 40, 645, 65, 349, 613, 468, 982, 314, 160, 675, 232, 794, 577, 571, 805, 317, 136, 860, 522, 45, 628, 178, 321, 482, 657, 114, 332, 728, 901, 290, 175, 876, 227, 130, 863, 773, 559, 301, 694, 460, 839, 952, 664, 851, 260, 729, 823, 880, 792, 964, 614, 821, 683, 364, 80, 875, 813, 951, 663, 344, 546, 918, 436, 451, 397, 670, 756, 512, 391, 70, 213, 896, 123, 858)

13）cache、persist

val c = sc.parallelize(List("Gnu", "Cat", "Rat", "Dog", "Gnu", "Rat"), 2)

c.getStorageLevel

res0: org.apache.spark.storage.StorageLevel = StorageLevel(false, false, false, false, 1)

c.cache

c.getStorageLevel

res2: org.apache.spark.storage.StorageLevel = StorageLevel(false, true, false, true, 1)

二、Key-Value型Transformation算子

1）mapValues

val a = sc.parallelize(List("dog", "tiger", "lion", "cat", "panther", "eagle"), 2)

val b = a.map(x => (x.length, x))

b.mapValues("x" + _ + "x").collect

res5: Array[(Int, String)] = Array((3,xdogx), (5,xtigerx), (4,xlionx), (3,xcatx), (7,xpantherx), (5,xeaglex))

2）combineByKey

val a = sc.parallelize(List("dog","cat","gnu","salmon","rabbit","turkey","wolf","bear","bee"), 3)

val b = sc.parallelize(List(1,1,2,2,2,1,2,2,2), 3)

val c = b.zip(a)

val d = c.combineByKey(List(_), (x:List[String], y:String) => y :: x, (x:List[String], y:List[String]) => x ::: y)

d.collect

res16: Array[(Int, List[String])] = Array((1,List(cat, dog, turkey)), (2,List(gnu, rabbit, salmon, bee, bear, wolf)))

3）reduceByKey

val a = sc.parallelize(List("dog", "cat", "owl", "gnu", "ant"), 2)

val b = a.map(x => (x.length, x))

b.reduceByKey(_ + _).collect

res86: Array[(Int, String)] = Array((3,dogcatowlgnuant))

val a = sc.parallelize(List("dog", "tiger", "lion", "cat", "panther", "eagle"), 2)

val b = a.map(x => (x.length, x))

b.reduceByKey(_ + _).collect

res87: Array[(Int, String)] = Array((4,lion), (3,dogcat), (7,panther), (5,tigereagle))

4）partitionBy

（对RDD进行分区操作）

5）cogroup

val a = sc.parallelize(List(1, 2, 1, 3), 1)

val b = a.map((_, "b"))

val c = a.map((_, "c"))

b.cogroup(c).collect

res7: Array[(Int, (Iterable[String], Iterable[String]))] = Array(

(2,(ArrayBuffer(b),ArrayBuffer(c))),

(3,(ArrayBuffer(b),ArrayBuffer(c))),

(1,(ArrayBuffer(b, b),ArrayBuffer(c, c)))

)

6）join

val a = sc.parallelize(List("dog", "salmon", "salmon", "rat", "elephant"), 3)

val b = a.keyBy(_.length)

val c = sc.parallelize(List("dog","cat","gnu","salmon","rabbit","turkey","wolf","bear","bee"), 3)

val d = c.keyBy(_.length)

b.join(d).collect

res0: Array[(Int, (String, String))] = Array((6,(salmon,salmon)), (6,(salmon,rabbit)), (6,(salmon,turkey)), (6,(salmon,salmon)), (6,(salmon,rabbit)), (6,(salmon,turkey)), (3,(dog,dog)), (3,(dog,cat)), (3,(dog,gnu)), (3,(dog,bee)), (3,(rat,dog)), (3,(rat,cat)), (3,(rat,gnu)), (3,(rat,bee)))

7）leftOutJoin

val a = sc.parallelize(List("dog", "salmon", "salmon", "rat", "elephant"), 3)

val b = a.keyBy(_.length)

val c = sc.parallelize(List("dog","cat","gnu","salmon","rabbit","turkey","wolf","bear","bee"), 3)

val d = c.keyBy(_.length)

b.leftOuterJoin(d).collect

res1: Array[(Int, (String, Option[String]))] = Array((6,(salmon,Some(salmon))), (6,(salmon,Some(rabbit))), (6,(salmon,Some(turkey))), (6,(salmon,Some(salmon))), (6,(salmon,Some(rabbit))), (6,(salmon,Some(turkey))), (3,(dog,Some(dog))), (3,(dog,Some(cat))), (3,(dog,Some(gnu))), (3,(dog,Some(bee))), (3,(rat,Some(dog))), (3,(rat,Some(cat))), (3,(rat,Some(gnu))), (3,(rat,Some(bee))), (8,(elephant,None)))

8）rightOutJoin

val a = sc.parallelize(List("dog", "salmon", "salmon", "rat", "elephant"), 3)

val b = a.keyBy(_.length)

val c = sc.parallelize(List("dog","cat","gnu","salmon","rabbit","turkey","wolf","bear","bee"), 3)

val d = c.keyBy(_.length)

b.rightOuterJoin(d).collect

res2: Array[(Int, (Option[String], String))] = Array((6,(Some(salmon),salmon)), (6,(Some(salmon),rabbit)), (6,(Some(salmon),turkey)), (6,(Some(salmon),salmon)), (6,(Some(salmon),rabbit)), (6,(Some(salmon),turkey)), (3,(Some(dog),dog)), (3,(Some(dog),cat)), (3,(Some(dog),gnu)), (3,(Some(dog),bee)), (3,(Some(rat),dog)), (3,(Some(rat),cat)), (3,(Some(rat),gnu)), (3,(Some(rat),bee)), (4,(None,wolf)), (4,(None,bear)))

三、Actions算子

1）foreach

val c = sc.parallelize(List("cat", "dog", "tiger", "lion", "gnu", "crocodile", "ant", "whale", "dolphin", "spider"), 3)

c.foreach(x => println(x + "s are yummy"))

lions are yummy

gnus are yummy

crocodiles are yummy

ants are yummy

whales are yummy

dolphins are yummy

spiders are yummy

2）saveAsTextFile

val a = sc.parallelize(1 to 10000, 3)

a.saveAsTextFile("mydata_a")

14/04/03 21:11:36 INFO FileOutputCommitter: Saved output of task 'attempt_201404032111_0000_m_000002_71' to file:/home/cloudera/Documents/spark-0.9.0-incubating-bin-cdh4/bin/mydata_a

3）saveAsObjectFile

val x = sc.parallelize(1 to 100, 3)

x.saveAsObjectFile("objFile")

val y = sc.objectFile[Int]("objFile")

y.collect

res52: Array[Int] = Array[Int] = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100)

4）collect

val c = sc.parallelize(List("Gnu", "Cat", "Rat", "Dog", "Gnu", "Rat"), 2)

c.collect

res29: Array[String] = Array(Gnu, Cat, Rat, Dog, Gnu, Rat)

5）collectAsMap

val a = sc.parallelize(List(1, 2, 1, 3), 1)

val b = a.zip(a)

b.collectAsMap

res1: scala.collection.Map[Int,Int] = Map(2 -> 2, 1 -> 1, 3 -> 3)

6）reduceByKeyLocally

val a = sc.parallelize(List("dog", "cat", "owl", "gnu", "ant"), 2)

val b = a.map(x => (x.length, x))

b.reduceByKey(_ + _).collect

res86: Array[(Int, String)] = Array((3,dogcatowlgnuant))

7）lookup

val a = sc.parallelize(List("dog", "tiger", "lion", "cat", "panther", "eagle"), 2)

val b = a.map(x => (x.length, x))

b.lookup(5)

res0: Seq[String] = WrappedArray(tiger, eagle)

8）count

val c = sc.parallelize(List("Gnu", "Cat", "Rat", "Dog"), 2)

c.count

res2: Long = 4

9）top

val c = sc.parallelize(Array(6, 9, 4, 7, 5, 8), 2)

c.top(2)

res28: Array[Int] = Array(9, 8)

10）reduce

val a = sc.parallelize(1 to 100, 3)

a.reduce(_ + _)

res41: Int = 5050

11）fold

val a = sc.parallelize(List(1,2,3), 3)

a.fold(0)(_ + _)

res59: Int = 6

12）aggregate

val rdd1 = sc.parallelize(List(1,2,3,4,5,6), 2)

// lets first print out the contents of the RDD with partition labels
def myfunc(index: Int, iter: Iterator[(Int)]) : Iterator[String] = {
iter.toList.map(x => "[partID:" + index + ", val: " + x + "]").iterator
}

rdd1.mapPartitionsWithIndex(myfunc).collect
rdd1.aggregate(0)(math.max(_, _), _ + _)

val rdd2 = sc.parallelize(List("a","b","c","d","e","f"), 2)

def myfunc2(index: Int, iter: Iterator[(String)]) : Iterator[String] = {
iter.toList.map(x => "[partID:" + index + ", val: " + x + "]").iterator
}

rdd2.mapPartitionsWithIndex(myfunc2).collect
rdd2.aggregate("")(_ + _,_ + _)
rdd2.aggregate("=")(_ + _,_ + _)

val rdd3 = sc.parallelize(List("12","23","345","4567"),2)
rdd3.aggregate("")((x,y)=>math.min(x.length,y.length).toString,(x,y)=> x+y)

val rdd4 = sc.parallelize(List("12","23","345",""),2)
rdd4.aggregate("")((x,y) =>math.min(x.length,y.length).toString,(x,y)=> x+y)

val rdd4 = sc.parallelize(List("12","23","","345"),2)
rdd4.aggregate("")((x,y) =>math.min(x.length,y.length).toString,(x,y)=> x+y)

猜你喜欢