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https://issues.apache.org/jira/browse/MAPREDUCE-2520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13036450#comment-13036450
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Chris Douglas commented on MAPREDUCE-2520:
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Which version of Hadoop are you using? I don't see this error in
[0.20|http://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.20/src/mapred/org/apache/hadoop/mapred/lib/InputSampler.java],
[0.21|http://svn.apache.org/repos/asf/hadoop/mapreduce/branches/branch-0.21/src/java/org/apache/hadoop/mapreduce/lib/partition/InputSampler.java],
or
[trunk|http://svn.apache.org/repos/asf/hadoop/mapreduce/trunk/src/java/org/apache/hadoop/mapreduce/lib/partition/InputSampler.java].
> InputSampler.RandomSampler only accepts Text keys
> -------------------------------------------------
>
> Key: MAPREDUCE-2520
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2520
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: William McNeill
> Priority: Minor
>
> I want to do a total sort on some data whose key type is Writable but not
> Text. I wrote an InputSampler.RandomSampler object following the example in
> the "Total Sort" section of Hadoop: The Definitive Guide. When I call
> InputSampler.writePartitionFile() I get a runtime class cast exception
> because my key type cannot be cast to Text. Specifically the issue seems to
> be the following section of InputSampler.getSample():
> K key = reader.getCurrentKey();
> ....
> Text keyCopy = WritableUtils.<Text>clone((Text)key,
> job.getConfiguration());
> You can only use a RandomSampler on data with Text keys despite the fact that
> InputSampler takes <Key, Value> generic parameters.
> InputSampler.getSample() should be changed to cast the key to type K instead
> of type Text.
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