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From Aaron Kimball <aa...@cloudera.com>
Subject Re: Does Using MultipleTextOutputFormat Require the Deprecated API?
Date Tue, 08 Dec 2009 21:39:02 GMT
Geoffry,

There are two MultipleOutputs implementations; one for the new API, one for
the old one.

The new API (org.apache.hadoop.mapreduce.lib.output.MultipleOutputs) does
not have a getCollector() method. This is intended to work with
org.apache.hadoop.mapreduce.Mapper and its associated Context object.

The old API implementation of MO
(org.apache.hadoop.mapred.lib.MultipleOutputs) is intended to work with
org.apache.hadoop.mapred.Mapper, Reporter, and friends.

If you're going to use the new org.apache.hadoop.mapreduce-based code, you
should not need to import anything in the mapred package. That having been
said -- I just realized that the new-API-compatible MultipleOutputs
implementation is not in Hadoop 0.20. It's only in the unreleased 0.21. If
you're using 0.20, you should probably stick with the old API for your
process.

Cheers,
- Aaron

On Tue, Dec 8, 2009 at 12:40 PM, Geoffry Roberts
<geoffry.roberts@gmail.com>wrote:

> All,
>
> This one has me stumped.
>
> What I want to do is output from my reducer multiple files, one for each
> key value. I also want to avoid any deprecated parts of the API.
>
> As suggested, I switched from using MultipleTextOutputFormat to
> MultipleOutputs but have run into an impasse.  MultipleOutputs' getCollector
> method requires a Reporter as a parameter, but as far as I can tell, the API
> doesn't support this.  The only reporter I can find is in the context
> object, but is declared protected.
>
> Am I stuck? or just missing something?
>
> My code:
>
> @Override
> public void reduce(Text key, Iterable<Text> values, Context context)
>                 throws IOException {
> String fileName = key.toString();
>              MultipleOutputs.addNamedOutput((JobConf)
> context.getConfiguration(), fileName, OutputFormat.class, Text.class,
> Text.class);
>             mos = new MultipleOutputs((JobConf)
> context.getConfiguration());
>             for (Text line : values) {
>
> // This is the problem line:
>                 mos.getCollector(fileName, <reporter goes here>).collect(
>                         key, line);
>             }
>
>             mos.close();
>
>          }
>
> On Mon, Oct 5, 2009 at 11:17 AM, Aaron Kimball <aaron@cloudera.com> wrote:
>
>> Geoffry,
>>
>> The new API comes with a related OF, called MultipleOutputs
>> (o.a.h.mapreduce.lib.output.MultipleOutputs). You may want to look into
>> using this instead.
>>
>> - Aaron
>>
>>
>> On Tue, Sep 29, 2009 at 4:44 PM, Geoffry Roberts <
>> geoffry.roberts@gmail.com> wrote:
>>
>>> All,
>>>
>>> What I want to do is output from my reducer multiple files one for each
>>> key value.
>>>
>>> Can this still be done in the current API?
>>>
>>> It seems that using MultipleTextOutputFormat requires one to use
>>> deprecated parts of API.
>>>
>>> It this correct?
>>>
>>> I would like to use the class or its equivalent and stay off anything
>>> deprecated.
>>>
>>> Is there a work around?
>>>
>>> In the current API one uses Job and a class derived from the classorg.apache.hadoop.mapreduce.OutputFormat.
>>> MultipleTextOutputFormat does not derive from this class.
>>>
>>> Job.setOutputFormatClass(Class<? extends org.apache.hadoop.mapreduce.
>>> OutputFormat>);
>>>
>>>
>>> In the Old, deprecated API, one uses JobConf and an implementation of the
>>> interface org.apache.hadoop.mapred.OutputFormat.
>>> MultipleTextOutputFormat is just such an implementation.
>>>
>>> JobConf.setOutputFormat(Class<? extends org.apache.hadoop.mapred .
>>> OutputFormat);
>>>
>>
>>
>

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