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7. sortByKey（true/false，[numTasks]）
7. sortByKey（true/false，[numTasks]）
创建一个pairRDD，按照key的大小，正序（true）和倒序（false）进行排序，默认正序
scala> val rdd7 = sc.makeRDD(Array((3,"aa"),(6,"cc"),(2,"bb"),(1,"dd")))
rdd7: org.apache.spark.rdd.RDD[(Int, String)] = ParallelCollectionRDD[4] at makeRDD at <console>:24
scala> rdd7.sortByKey(true).collect
res4: Array[(Int, String)] = Array((1,dd), (2,bb), (3,aa), (6,cc))
scala> rdd7.sortByKey(false).collect
res5: Array[(Int, String)] = Array((6,cc), (3,aa), (2,bb), (1,dd))8. mapValues
针对（K，V）的map形式数据，无视key，只对V进行操作
eg：创建一个pairRDD，将Value添加“~”
scala> val rdd8 = sc.makeRDD(Array((1,"a"),(1,"d"),(2,"b"),(3,"c")))
rdd8: org.apache.spark.rdd.RDD[(Int, String)] = ParallelCollectionRDD[11] at makeRDD at <console>:24
scala> rdd8.mapValues(_+"~").collect
res6: Array[(Int, String)] = Array((1,a~), (1,d~), (2,b~), (3,c~))9. join（内联结）
将两个相同key的RDD（K，V）和（K，W），返回（K，(V，W)）的RDD；内联结，求交集
scala> val rddA = sc.makeRDD(Array((1,"a"),(2,"b"),(3,"c")))
rddA: org.apache.spark.rdd.RDD[(Int, String)] = ParallelCollectionRDD[14] at makeRDD at <console>:24
scala> val rddB = sc.makeRDD(Array((1,6),(2,7),(3,8),(4,9),(5,10)))
rddB: org.apache.spark.rdd.RDD[(Int, Int)] = ParallelCollectionRDD[15] at makeRDD at <console>:24
scala> rddA.join(rddB).collect
res3: Array[(Int, (String, Int))] = Array((1,(a,6)), (2,(b,7)), (3,(c,8)))只返回主表中key对应的数据联结
10. cogroup（外联结）
将两个RDD（K，V）、（K，W）联结，返回（K，(Iterable<V>,Iterable<W>)）类型的RDD
eg：创建两个pairRDD，将key相同的数据聚合到一个迭代器
scala> val rdd1 = sc.makeRDD(Array((1,"a"),(2,"b"),(3,"c")))
rdd1: org.apache.spark.rdd.RDD[(Int, String)] = ParallelCollectionRDD[9] at makeRDD at <console>:24
scala> val rdd2 = sc.makeRDD(Array((1,2),(2,3),(3,4),(4,5),(5,6)))
rdd2: org.apache.spark.rdd.RDD[(Int, Int)] = ParallelCollectionRDD[10] at makeRDD at <console>:24
scala> rdd1.cogroup(rdd2).collect
res2: Array[(Int, (Iterable[String], Iterable[Int]))] = Array((1,(CompactBuffer(a),CompactBuffer(2))), (2,(CompactBuffer(b),CompactBuffer(3))), (3,(CompactBuffer(c),CompactBuffer(4))), (4,(CompactBuffer(),CompactBuffer(5))), (5,(CompactBuffer(),CompactBuffer(6))))
主从表中所有key对应的数据都会出来，key对应的主表数据缺失的用( )表示了