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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-960) Unnecessary copy in mapreduce.lib.input.KeyValueLineRecordReader
Date Tue, 08 Sep 2009 00:47:57 GMT
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
            Reporter: Chris Douglas
            Assignee: Chris Douglas


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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