Saisai Shao created SPARK-3032:
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Summary: Potential bug when running sort-based shuffle with
sorting using TimSort
Key: SPARK-3032
URL: https://issues.apache.org/jira/browse/SPARK-3032
Project: Spark
Issue Type: Bug
Components: Shuffle
Affects Versions: 1.1.0
Reporter: Saisai Shao
When using SparkPerf's aggregate-by-key workload to test sort-based shuffle,
data type for key and value is (String, String), always meet this issue:
{noformat}
java.lang.IllegalArgumentException: Comparison method violates its general
contract!
at
org.apache.spark.util.collection.Sorter$SortState.mergeLo(Sorter.java:755)
at
org.apache.spark.util.collection.Sorter$SortState.mergeAt(Sorter.java:493)
at
org.apache.spark.util.collection.Sorter$SortState.mergeCollapse(Sorter.java:420)
at
org.apache.spark.util.collection.Sorter$SortState.access$200(Sorter.java:294)
at org.apache.spark.util.collection.Sorter.sort(Sorter.java:128)
at
org.apache.spark.util.collection.SizeTrackingPairBuffer.destructiveSortedIterator(SizeTrackingPairBuffer.scala:83)
at
org.apache.spark.util.collection.ExternalSorter.spillToMergeableFile(ExternalSorter.scala:323)
at
org.apache.spark.util.collection.ExternalSorter.spill(ExternalSorter.scala:271)
at
org.apache.spark.util.collection.ExternalSorter.maybeSpill(ExternalSorter.scala:249)
at
org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:220)
at
org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:85)
at
org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:68)
at
org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
at org.apache.spark.scheduler.Task.run(Task.scala:54)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:199)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
{noformat}
Seems the current partitionKeyComparator which use hashcode of String as key
comparator break some sorting contracts.
Also I tested using data type Int as key, this is OK to pass the test, since
hashcode of Int is its self. So I think potentially partitionDiff + hashcode of
String may break the sorting contracts.
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