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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3380) need comparators in serializer framework
Date Fri, 23 May 2008 18:25:56 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3380?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12599451#action_12599451
] 

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

> serializationFactory.getSerialization(IntWritable) equals serializationFactory.getSerialization(DoubleWritable)

No, that's not required and not the case with the current implementation.

> Anyway, aside from this, what is the benefit of tying getComparator() to serialization
[...]

A RawComparator compares serialized data, not objects.


> 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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