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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5494) IFile.Reader should have a nextRawKey/nextRawValue
Date Wed, 08 Apr 2009 05:35:13 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12696895#action_12696895
] 

Devaraj Das commented on HADOOP-5494:
-------------------------------------

ant tests/test-patch passed on my box.

> IFile.Reader should have a nextRawKey/nextRawValue
> --------------------------------------------------
>
>                 Key: HADOOP-5494
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5494
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.18.0
>            Reporter: Devaraj Das
>            Assignee: Devaraj Das
>             Fix For: 0.21.0
>
>         Attachments: 5494-1.patch, 5494-2.patch, 5494-3.patch, 5494-4.patch
>
>
> Merger.Segment has only the next() method defined which internally calls next(key,value)
on the underlying IFile stream. This would read both the key and the value bytes. It would
be good to have Merger.Segment.nextRawKey(), that would read only the key and delay reading
the value until needed (in Merger.MergeQueue.next()) via a new method Merger.Segment.nextRawValue().

> This would mean that we load only one value bytes at a time, and hence would incur potentially
much less (depending on how big the values are) on the memory footprint.

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