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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3380) need comparators in serializer framework
Date Tue, 20 May 2008 16:21:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3380?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12598348#action_12598348
] 

Doug Cutting commented on HADOOP-3380:
--------------------------------------

> Note that getComparator() takes the class as an argument [ ... ]

That makes sense, but I had assumed that the Serialization could keep a pointer to the class
and then use that in its implementation of getComparator() to look up a registered comparator.
 Applications would not need to pass a class to Serialization#getComparator(), since Serializeation
is already parameterized by class.


> need comparators in serializer framework
> ----------------------------------------
>
>                 Key: HADOOP-3380
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3380
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: io
>            Reporter: Doug Cutting
>         Attachments: comparator_wip1.patch, comparator_wip1.patch
>
>
> The new serialization framework permits Hadoop to incorporate different serialization
systems, including Hadoop's Writable, Thrift, Java Serialization, etc.  It provides a generic,
extensible means (SerializationFactory) to create serializers and deserializers for arbitrary
Java classes.  However it does not include a generic means to create comparators for these
classes.  Comparators are required for MapReduce keys and many other computations.  Thus we
should enhance the serialization framwork to provide comparators too.

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