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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-80) binary key
Date Wed, 15 Mar 2006 23:41:58 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-80?page=comments#action_12370606 ] 

Doug Cutting commented on HADOOP-80:
------------------------------------

If we think that the default java hash function is bad, then we should probably switch it
in all of the places where we hash, e.g., in UTF8, here, etc.  For now I will: (a) add a static
hashBytes() method to WritableComparable, use it in BytesWritable().  Then, if we someday
decide to change the hash function then we'll have a single place to do it.  Allocating a
new digester per call to hashCode() seems expensive (although I have not benchmarked this).

MapReduce does use the hash function by default for partitioning, but HashMaps will also use
it, so MapReduce is not the only client.

> binary key
> ----------
>
>          Key: HADOOP-80
>          URL: http://issues.apache.org/jira/browse/HADOOP-80
>      Project: Hadoop
>         Type: New Feature
>   Components: io
>     Versions: 0.1
>     Reporter: Owen O'Malley
>     Assignee: Owen O'Malley
>      Fix For: 0.1
>  Attachments: binary-key-2.patch, binary-key.patch
>
> I needed a binary key type, so I extended BytesWritable to be comparable also.

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