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https://issues.apache.org/jira/browse/HADOOP-1986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12531962
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Owen O'Malley commented on HADOOP-1986:
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But it is strictly more powerful allowing a serializer per a class (or
hierarchy). Furthermore, it means you only have to configure the small number
of serializers rather than worry about which context you need to set which
serializer for. I think it is more confusing if you have to say:
FileInputFormat.setSerializer(conf, Bar.class);
job.setMapOutputSerializer(Foo.class);
FileOutputFormat.setSerializer(conf, Baz.class);
and it still would prevent you from mixing serializers between keys and values.
Unless you are proposing the even more verbose:
FileInputFormat.setKeySerializer(conf, BarKey.class);
FileInputFormat.setValueSerializer(conf, BarValue.class);
job.setMapOutputKeySerializer(FooKey.class);
job.setMapOutputValueSerializer(FooValue.class);
FileOutputFormat.setKeySerializer(conf, BazKey.class);
FileOutputFormat.setValueSerializer(conf, BazValue.class);
I think the Serializers for a given type are constant, rather than the
Serializers for a given context being constant.
> Add support for a general serialization mechanism for Map Reduce
> ----------------------------------------------------------------
>
> Key: HADOOP-1986
> URL: https://issues.apache.org/jira/browse/HADOOP-1986
> Project: Hadoop
> Issue Type: New Feature
> Components: mapred
> Reporter: Tom White
> Fix For: 0.16.0
>
>
> Currently Map Reduce programs have to use WritableComparable-Writable
> key-value pairs. While it's possible to write Writable wrappers for other
> serialization frameworks (such as Thrift), this is not very convenient: it
> would be nicer to be able to use arbitrary types directly, without explicit
> wrapping and unwrapping.
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