[GitHub] [spark] cloud-fan commented on a change in pull request #28895: [SPARK-32055][CORE][SQL] Unify getReader and getReaderForRange in ShuffleManager

[GitBox <gi...@apache.org>]

cloud-fan commented on a change in pull request #28895:
URL: https://github.com/apache/spark/pull/28895#discussion_r443940713



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File path: core/src/main/scala/org/apache/spark/shuffle/ShuffleManager.scala
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@@ -43,26 +44,16 @@ private[spark] trait ShuffleManager {
       context: TaskContext,
       metrics: ShuffleWriteMetricsReporter): ShuffleWriter[K, V]
 
-  /**
-   * Get a reader for a range of reduce partitions (startPartition to endPartition-1, inclusive).
-   * Called on executors by reduce tasks.
-   */
-  def getReader[K, C](
-      handle: ShuffleHandle,
-      startPartition: Int,
-      endPartition: Int,
-      context: TaskContext,
-      metrics: ShuffleReadMetricsReporter): ShuffleReader[K, C]
-
   /**
    * Get a reader for a range of reduce partitions (startPartition to endPartition-1, inclusive) to
-   * read from map output (startMapIndex to endMapIndex - 1, inclusive).
+   * read from a range of map outputs which specified by mapIndexRange(startMapIndex to
+   * endMapIndex-1, inclusive).
+   *
    * Called on executors by reduce tasks.
    */
-  def getReaderForRange[K, C](
+  def getReader[K, C](
       handle: ShuffleHandle,
-      startMapIndex: Int,
-      endMapIndex: Int,
+      mapIndexRange: Array[MapStatus] => (Int, Int),

Review comment:
       It's a function only because we need to know the total number of mappers? Maybe we can still use `startMapIndex: Int` and `endMapIndex: Int`, caller side can use `Int.Max` as `endMapIndex`, to indicate that it wants to read all the mappers.




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