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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1231) Add generics to Mapper and Reducer interfaces
Date Mon, 18 Jun 2007 18:04:26 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12505906
] 

Doug Cutting commented on HADOOP-1231:
--------------------------------------

I think it's simply that MapReduce input keys are never compared, while output keys are. 
(Note also that SequenceFile keys are not required to be Comparable.)  So, in some sense,
the anomalies are Mapper#map() and RecordReader#createKey(), which add an unneeded restriction.
 But perhaps such minimalism only complicates things.

> 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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