RDD Lineage（又稱為RDD運算圖或RDD依賴關係圖）是RDD所有父RDD的graph（圖）。它是在RDD上執行transformations函式並建立logical execution plan（邏輯執行計劃）的結果。它是RDD的邏輯執行計劃。
注意： execution DAG或physical execution plan（物理執行計劃）是DAG of stages（stage的DAG）。

上圖是執行以下語句得到的RDD Lineage結果：

val r00 = sc.parallelize(0 to 9)
val r01 = sc.parallelize(0 to 90 by 10
 
)
val r10 = r00 cartesian r01
val r11 = r00.map(n => (n, n))
val r12 = r00 zip r01
val r13 = r01.keyBy(_ / 20)
val r20 = Seq(r11, r12, r13).foldLeft(r10)(_ union _)

我們可以執行toDebugString列印RDD的Lineage：

scala> r00.toDebugString
res5: String = (20) ParallelCollectionRDD[0] at parallelize at <console>:27 []

scala> r01.toDebugString
res6: String = (20
 
) ParallelCollectionRDD[1] at parallelize at <console>:27 []    

scala> r12.toDebugString
res9: String = 
(20) ZippedPartitionsRDD2[4] at zip at <console>:31 []
 | ParallelCollectionRDD[0] at parallelize at <console>:27 []
 | ParallelCollectionRDD[1] at parallelize at <console>:27
 
 []
scala> r13.toDebugString
res10: String = 
(20) MapPartitionsRDD[5] at keyBy at <console>:29 []
 | ParallelCollectionRDD[1] at parallelize at <console>:27 []

scala> r20.toDebugString
res11: String = 
(460) UnionRDD[8] at union at <console>:39 []
  | UnionRDD[7] at union at <console>:39 []
  | UnionRDD[6] at union at <console>:39 []
  | CartesianRDD[2] at cartesian at <console>:31 []
  | ParallelCollectionRDD[0] at parallelize at <console>:27 []
  | ParallelCollectionRDD[1] at parallelize at <console>:27 []
  | MapPartitionsRDD[3] at map at <console>:29 []
  | ParallelCollectionRDD[0] at parallelize at <console>:27 []
  | ZippedPartitionsRDD2[4] at zip at <console>:31 []
  | ParallelCollectionRDD[0] at parallelize at <console>:27 []
  | ParallelCollectionRDD[1] at parallelize at <console>:27 []
  | MapPartitionsRDD[5] at keyBy at <console>:29 []
  | ParallelCollectionRDD[1] at parallelize at <console>:27 []

從以上輸出可以看出，RDD譜系圖是在呼叫action函式後需要執行哪些transformation（變換）的graph(圖)。

toDebugString

函式原型：

def toDebugString: String

通過此函式可以獲取RDD的Lineage列印輸出。

設定列印Lineage

引數：spark.logLineage
預設值：false
設定為true時，會在執行中打印出RDD的Lineage。

Logical Execution Plan（邏輯執行計劃）

logical execution plan（邏輯執行計劃）從最早（頭結點-沒有父結點的節點）的RDD（不依賴於其他RDD或引用快取資料的RDD）開始，並以生成被執行的action操作結果的RDD結束。