Spark算子总结及案例
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
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
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
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 z = 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 } z.mapPartitionsWithIndex(myfunc).collect res28: Array[String] = Array([partID:0, val: 1], [partID:0, val: 2], [partID:0, val: 3], [partID:1, val: 4], [partID:1, val: 5], [partID:1, val: 6]) z.aggregate(0)(math.max(_, _), _ + _) res40: Int = 9
参考：http://homepage.cs.latrobe.edu.au/zhe/ZhenHeSparkRDDAPIExamples.html
当神已无能为力，那便是魔渡众生
