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[SPARK-7181][CORE]fix inifite loop in Externalsorter's mergeWithAggregation #5737

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[SPARK-7181][CORE]fix inifite loop in Externalsorter's mergeWithAggregation #5737

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3 changes: 2 additions & 1 deletion core/src/main/scala/org/apache/spark/util/collection/ExternalSorter.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -525,7 +525,8 @@ private[spark] class ExternalSorter[K, V, C](
val k = elem._1
var c = elem._2
while (sorted.hasNext && sorted.head._1 == k) {
c = mergeCombiners(c, sorted.head._2)
val pair = sorted.next()
c = mergeCombiners(c, pair._2)
}
(k, c)
}
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5 changes: 4 additions & 1 deletion core/src/test/scala/org/apache/spark/util/collection/ExternalSorterSuite.scala
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Expand Up @@ -506,7 +506,10 @@ class ExternalSorterSuite extends FunSuite with LocalSparkContext with PrivateMe
val agg = new Aggregator[Int, Int, Int](i => i, (i, j) => i + j, (i, j) => i + j)
val ord = implicitly[Ordering[Int]]
val sorter = new ExternalSorter(Some(agg), Some(new HashPartitioner(3)), Some(ord), None)
sorter.insertAll((0 until 100000).iterator.map(i => (i / 2, i)))

// avoid combine before spill
sorter.insertAll((0 until 50000).iterator.map(i => (i , 2 * i)))
sorter.insertAll((0 until 50000).iterator.map(i => (i, 2 * i + 1)))
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does this actually run the case that you modified? (i.e. did this modified test fail before your fix?)

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Yes, it failed on my computer(this testcase didn't stop). I set the memory limit to a small value on my computer to ganrantee spills. I think we can also set spark.shuffle.memoryFraction to a small value to do this. The origin value of spark.shuffle.memoryFraction is 0.001, I don't know if it can ganrantee spills. If not, we should change it to a smaller value.

val results = sorter.partitionedIterator.map{case (p, vs) => (p, vs.toSet)}.toSet
val expected = (0 until 3).map(p => {
(p, (0 until 50000).map(i => (i, i * 4 + 1)).filter(_._1 % 3 == p).toSet)
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