InverseMapper causes IntWritable type to collected as Text
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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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