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[SPARK-4691][shuffle] Restructure a few lines in shuffle code #3553

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[SPARK-4691][shuffle] Restructure a few lines in shuffle code #3553

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d8f52dc
code optimization for judgement
Dec 2, 2014
10d0cf0
change a elegant way
Dec 3, 2014
bf7b14d
change a elegant way for SortShuffleWriter.scala
Dec 4, 2014
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2 changes: 1 addition & 1 deletion core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ private[spark] class HashShuffleReader[K, C](
} else {
new InterruptibleIterator(context, dep.aggregator.get.combineValuesByKey(iter, context))
}
} else if (dep.aggregator.isEmpty && dep.mapSideCombine) {
} else if (dep.mapSideCombine) {
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I think the previous way is much more clear and obvious from my understanding :-).

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"if(dep.aggregator.isDefined) else if (dep.aggregator.isEmpty)" seems duplicate. isEmpty == !isDefined
We need to do another one more judgement for "dep.aggregator.isEmpty".
Also, in SortShuffleWriter.scala, i think "dep.aggregator.isEmpty" is better than "!dep.aggregator.isDefined".

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Could also write this as

if (dep.aggregator.isDefined) {
  ...
} else {
  require(!dep.mapSideCombine, "Map-side combine requested without Aggregator specified!")

  // Convert the Product2s to pairs since this is what downstream RDDs currently expect
  iter.asInstanceOf[Iterator[Product2[K, C]]].map(pair => (pair._1, pair._2))
}

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Yes, this seems simple and elegant

throw new IllegalStateException("Aggregator is empty for map-side combine")
} else {
// Convert the Product2s to pairs since this is what downstream RDDs currently expect
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2 changes: 1 addition & 1 deletion core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleWriter.scala
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Expand Up @@ -56,7 +56,7 @@ private[spark] class HashShuffleWriter[K, V](
} else {
records
}
} else if (dep.aggregator.isEmpty && dep.mapSideCombine) {
} else if (dep.mapSideCombine) {
throw new IllegalStateException("Aggregator is empty for map-side combine")
} else {
records
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2 changes: 1 addition & 1 deletion core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleWriter.scala
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Expand Up @@ -50,7 +50,7 @@ private[spark] class SortShuffleWriter[K, V, C](
/** Write a bunch of records to this task's output */
override def write(records: Iterator[_ <: Product2[K, V]]): Unit = {
if (dep.mapSideCombine) {
if (!dep.aggregator.isDefined) {
if (dep.aggregator.isEmpty) {
throw new IllegalStateException("Aggregator is empty for map-side combine")
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could change this guy to a require as well, and maybe change the message too

}
sorter = new ExternalSorter[K, V, C](
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