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From vaibhav negi <sssssssena...@gmail.com>
Subject Hive Error: while executing select count(*)
Date Tue, 28 Sep 2010 14:37:31 GMT
Hi,

I am using hadoop version 0.20.2

While running query "select count(*) from table;" on Hive,i am getting this
error

FAILED: Execution Error, return code 2 from
org.apache.hadoop.hive.ql.exec.MapRedTask

Error in task tracker logs says :-

Error: java.lang.NullPointerException
 at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)

On debugging i found that ReduceTask.java:2683  line is using host which is
coming null

ReduceTask.java:2683 ---
 List loc = mapLocations.get(host);

One user in Hadoop Forum says HADOOP-4744 should be included in hadoop. Is
this patch required for hadoop 0.20.2 ?
How to add patch?

Is this an issue with /etc/hosts file?

Please help

Regards
Vaibhav Negi

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