spark中各种连接操作以及有用方法「建议收藏」

 val a = sc.parallelize(Array(("123",4.0),("456",9.0),("789",9.0))
     val b = sc.parallelize(Array(("123",8.0),("789",10)))

    val c = a.join(b)
    c.foreach(println)
    /*
    (123,(4.0,8.0))
    (789,(9.0,10))
     */
    val d = a.cogroup(b)
    d.foreach(println)
    /*
    (456,(CompactBuffer(9.0),CompactBuffer()))
    (123,(CompactBuffer(4.0),CompactBuffer(8.0)))
    (789,(CompactBuffer(9.0),CompactBuffer(10)))
    */
    val e = a.leftOuterJoin(b)
    e.foreach(println)
    /*
      (456,(9.0,None))
      (123,(4.0,Some(8.0)))
      (789,(9.0,Some(10)))
      */
    val f = a.fullOuterJoin(b)
    f.foreach(println)
    /*
      (456,(Some(9.0),None))
      (123,(Some(4.0),Some(8.0)))
      (789,(Some(9.0),Some(10)))
      */
    val g = a.cartesian(b)
    g.foreach(println)
    /*
((123,4.0),(123,8.0))
((123,4.0),(789,10))
((456,9.0),(123,8.0))
((456,9.0),(789,10))
((789,9.0),(123,8.0))
((789,9.0),(789,10))
      */
    /*val h = a.coalesce(6,true)
    h.foreach(println)
    a.dependencies.foreach(println)*/
    val i = a.keyBy{case (k,v)=>("haha",234)}
    i.foreach(println)
    /*
      ((haha,234),(123,4.0))
      ((haha,234),(456,9.0))
      ((haha,234),(789,9.0))
     */