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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1231) Add generics to Mapper and Reducer interfaces
Date Sun, 17 Jun 2007 21:38:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12505628

Tom White commented on HADOOP-1231:

RecordReader's next() method takes a Writable key (and a Writable value), whereas RecordWriter
takes a WritableComparable key. Mapper and Reducer have WritableComparable keys too. Does
anyone know the reason for this? I think it could be changed to be WritableComparable without
breaking any Hadoop code (this would be desirable to avoid complicating the generic types)
but would it break any code outside Hadoop? Interestingly the createKey() method returns a
WritableComparable, so my guess it not, but I'm interested to hear what folks think.

> Add generics to Mapper and Reducer interfaces
> ---------------------------------------------
>                 Key: HADOOP-1231
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1231
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Owen O'Malley
>            Assignee: Tom White
> By making the input and output types of the Mapper and Reducers generic, we can get the
information from the classes and not require the user to set them in the configuration.

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