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Date: Wed, 9 Sep 2009 03:49:57 -0700 (PDT)
From: "Tom White (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-960) Unnecessary copy in
 mapreduce.lib.input.KeyValueLineRecordReader
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753023#action_12753023 ] 

Tom White commented on MAPREDUCE-960:
-------------------------------------

+1

KeyValueLineRecordReader is tested by TestMRKeyValueTextInputFormat so no new test is needed.

> Unnecessary copy in mapreduce.lib.input.KeyValueLineRecordReader
> ----------------------------------------------------------------
>
>                 Key: MAPREDUCE-960
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-960
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>    Affects Versions: 0.21.0
>            Reporter: Chris Douglas
>            Assignee: Chris Douglas
>         Attachments: M960-0.patch
>
>
> KeyValueLineRecordReader effects the copy from the line to the key/value by creating separate arrays:
> {noformat}
>       int keyLen = pos;
>       byte[] keyBytes = new byte[keyLen];
>       System.arraycopy(line, 0, keyBytes, 0, keyLen);
>       int valLen = lineLen - keyLen - 1;
>       byte[] valBytes = new byte[valLen];
>       System.arraycopy(line, pos + 1, valBytes, 0, valLen);
>       key.set(keyBytes);
>       value.set(valBytes);
> {noformat}
> Since set triggers another copy and Text has a set taking {{byte[], off, len}}, the intermediate copy can be avoided

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