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https://issues.apache.org/jira/browse/SPARK-20943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16033988#comment-16033988
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CanBin Zheng edited comment on SPARK-20943 at 6/2/17 1:11 AM:
--------------------------------------------------------------
Look at there two cases.
{code}
//Has Aggregator defined
@Test
def testGroupByKeyUsingBypassMergeSort(): Unit = {
val data = List("Hello", "World", "Hello", "One", "Two")
val rdd = sc.parallelize(data).map((_, 1)).groupByKey(2)
rdd.collect()
}
//Has Ordering defined
@Test
def testShuffleWithKeyOrderingUsingBypassMergeSort(): Unit = {
val data = List("Hello", "World", "Hello", "One", "Two")
val rdd = sc.parallelize(data).map((_, 1))
val ord = implicitly[Ordering[String]]
val shuffledRDD = new ShuffledRDD[String, Int, Int](rdd, new
HashPartitioner(2)).setKeyOrdering(ord)
shuffledRDD.collect()
}
{code}
was (Author: canbinzheng):
Look at there two cases.
`//Has Aggregator defined
@Test
def testGroupByKeyUsingBypassMergeSort(): Unit = {
val data = List("Hello", "World", "Hello", "One", "Two")
val rdd = sc.parallelize(data).map((_, 1)).groupByKey(2)
rdd.collect()
}
//Has Ordering defined
@Test
def testShuffleWithKeyOrderingUsingBypassMergeSort(): Unit = {
val data = List("Hello", "World", "Hello", "One", "Two")
val rdd = sc.parallelize(data).map((_, 1))
val ord = implicitly[Ordering[String]]
val shuffledRDD = new ShuffledRDD[String, Int, Int](rdd, new
HashPartitioner(2)).setKeyOrdering(ord)
shuffledRDD.collect()
}`
> Correct BypassMergeSortShuffleWriter's comment
> ----------------------------------------------
>
> Key: SPARK-20943
> URL: https://issues.apache.org/jira/browse/SPARK-20943
> Project: Spark
> Issue Type: Improvement
> Components: Documentation, Shuffle
> Affects Versions: 2.1.1
> Reporter: CanBin Zheng
> Priority: Trivial
> Labels: starter
>
> There are some comments written in BypassMergeSortShuffleWriter.java about
> when to select this write path， the three required conditions are described
> as follows:
> 1. no Ordering is specified, and
> 2. no Aggregator is specified, and
> 3. the number of partitions is less than
> spark.shuffle.sort.bypassMergeThreshold
> Obviously, the conditions written are partially wrong and misleading, the
> right conditions should be:
> 1. map-side combine is false, and
> 2. the number of partitions is less than
> spark.shuffle.sort.bypassMergeThreshold
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