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From "Saad Patel (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-3962) InverseMapper causes IntWritable type to collected as Text
Date Fri, 02 Mar 2012 23:32:54 GMT
InverseMapper causes IntWritable type to collected as Text
----------------------------------------------------------

                 Key: MAPREDUCE-3962
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3962
             Project: Hadoop Map/Reduce
          Issue Type: Bug
    Affects Versions: 1.0.0
            Reporter: Saad Patel


When using the org.apache.hadoop.mapred.lib.InverseMapper, key,values are inversed as expected.
For example (Text,IntWritable) will get inversed. However, output key,value only works if
you use (Text, Text). Below is an example, where I was chaining 2 jobs:

Job 1:
public static class Reduce extends MapReduceBase implements Reducer<Text, IntWritable,
Text, IntWritable>{...}

Job 2:
conf.setMapperClass(InverseMapper.class);
public static class Reduce extends MapReduceBase implements Reducer<IntWritable, Text,
Text, IntWritable> {...} //I would expect this to work. When I do this, I get
java.lang.ClassCastException: org.apache.hadoop.io.Text cannot be cast to org.apache.hadoop.io.IntWritable

To re-inverse my key,values, I had to do this:
public static class Reduce extends MapReduceBase implements Reducer<Text, Text, Text, Text>

Notice that in order for the reducer to properly accept key,values, I had to indicate the
key as Text.




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