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From "William McNeill (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-2520) InputSampler.RandomSampler only accepts Text keys
Date Thu, 19 May 2011 17:02:47 GMT
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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