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MapReduce >> mail # user >> Re: How to output according to the key in reducer?


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Hemanth Yamijala 2012-09-17, 08:08
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Re: How to output according to the key in reducer?
Hi
Maybe you can refer to
http://hadoop.apache.org/docs/r1.0.3/api/org/apache/hadoop/mapred/lib/MultipleSequenceFileOutputFormat.html

or

http://hadoop.apache.org/docs/r1.0.3/api/org/apache/hadoop/mapred/lib/MultipleTextOutputFormat.html

example like this

  public static class GeneratorOutputFormat extends
      MultipleSequenceFileOutputFormat<IntWritable,Text> {
    // generate a filename based on the segnum stored for this text
    protected String generateFileNameForKeyValue(IntWritable key, Text
value,
        String name) {
      return "ID_" + key.get() + ".dat";
    }

  }

On Mon, Sep 17, 2012 at 3:16 PM, Jason Yang <[EMAIL PROTECTED]>wrote:

> Hi, all
>
> I was wondering how to write all the input with the same key to a single
> file in the reducer ?
>
> say, I got some intermediate outputs from mappers like that:
> key     value
> --------------------
> 1   annie
> 2   Jason
> 1   andy
> 2   Joey
> 1   andrew
> ...
>
> and I would like write all the intermediate outputs with key 1 to file
> "ID_1.dat", and all the intermediate outputs with key 2 to file "ID_2.data".
>
> how could I achieve that?
>
> --
> YANG, Lin
>
>
--
Don't Grow Old, Grow Up... :-)
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Jason Yang 2012-09-17, 09:23