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Date: Wed, 1 Feb 2012 18:03:01 +0000 (UTC)
From: "Eli Collins (Commented) (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Commented] (MAPREDUCE-3768) MR-2450 introduced a
 significant performance regression
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-3768?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13198007#comment-13198007 ] 

Eli Collins commented on MAPREDUCE-3768:
----------------------------------------

Here's a jstack during test execution. Possible that it could be a bug in Hive but more likely an issue of 2450 interacting with the LocalJobRunner.

{noformat}
"LocalJobRunner Map Task Executor #0" prio=5 tid=102804800 nid=0x10ef1e000 in Object.wait() [10ef1d000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <7bd6c6890> (a java.lang.Object)
	at java.lang.Object.wait(Object.java:485)
	at org.apache.hadoop.mapred.Task$TaskReporter.stopCommunicationThread(Task.java:726)
	- locked <7bd6c6890> (a java.lang.Object)
	at org.apache.hadoop.mapred.Task.done(Task.java:935)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:332)
	at org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:232)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:680)
{noformat}
                
> MR-2450 introduced a significant performance regression
> -------------------------------------------------------
>
>                 Key: MAPREDUCE-3768
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3768
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>    Affects Versions: 0.23.1
>            Reporter: Eli Collins
>            Priority: Blocker
>
> MAPREDUCE-2450 introduced, or at least triggers, a significant performance regression in Hive. With MR-2450 the execution time of TestCliDriver.skewjoin goes from 2 minutes to 15 minutes. Reverting this change from the build fixes the issue.
> Here's the relevant query:
> {noformat}
> FROM src src1 JOIN src src2 ON (src1.key = src2.key)
> INSERT OVERWRITE TABLE dest_j1 SELECT src1.key, src2.value; 
> {noformat}
> You can reproduce this by running the following from Hive 8.0 against Hadoop built from branch-23. 
> {noformat}
> ant very-clean package test -Dtestcase=TestCliDriver -Dqfile=skewjoin.q
> {noformat}

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