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Date: Mon, 3 Mar 2008 12:18:51 -0800 (PST)
From: "Doug Cutting (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-1230) Replace parameters with context
 objects in Mapper, Reducer, Partitioner, InputFormat, and OutputFormat
 classes
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    [ https://issues.apache.org/jira/browse/HADOOP-1230?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574724#action_12574724 ] 

Doug Cutting commented on HADOOP-1230:
--------------------------------------

> I also changed the generic parameters to all caps although it looks ugly to my eyes.

Might capitalization be a good compromise?  Also I slightly prefer In/Out before Key/Value rather than after in these names, i.e., InKeyClass, InValClass, OutKeyClass & OutValClass to KeyInClass, ValInClass, KeyOutClass, & ValOutClass.

> I didn't add the raw stuff yet [ ... ]

That's fine.  It should probably be a separate issue.


> Replace parameters with context objects in Mapper, Reducer, Partitioner, InputFormat, and OutputFormat classes
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-1230
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1230
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Owen O'Malley
>            Assignee: Owen O'Malley
>         Attachments: context-objs-2.patch, context-objs.patch
>
>
> This is a big change, but it will future-proof our API's. To maintain backwards compatibility, I'd suggest that we move over to a new package name (org.apache.hadoop.mapreduce) and deprecate the old interfaces and package. Basically, it will replace:
> package org.apache.hadoop.mapred;
> public interface Mapper extends JobConfigurable, Closeable {
>   void map(WritableComparable key, Writable value, OutputCollector output, Reporter reporter) throws IOException;
> }
> with:
> package org.apache.hadoop.mapreduce;
> public interface Mapper extends Closable {
>   void map(MapContext context) throws IOException;
> }
> where MapContext has the methods like getKey(), getValue(), collect(Key, Value), progress(), etc.

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