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Posted to common-dev@hadoop.apache.org by "Doug Cutting (JIRA)" <ji...@apache.org> on 2006/09/13 23:55:23 UTC

[jira] Commented: (HADOOP-531) Need to sort on more than the primary key

    [ http://issues.apache.org/jira/browse/HADOOP-531?page=comments#action_12434552 ] 
            
Doug Cutting commented on HADOOP-531:
-------------------------------------

The two ideas that have been discussed related to this are:

1. Making reduce value iterators cloneable.
2. Permitting one to specify a different comparator for sorting than for dividing keys when reducing.

Are there issues in Jira for either of these yet?


> Need to sort on more than the primary key
> -----------------------------------------
>
>                 Key: HADOOP-531
>                 URL: http://issues.apache.org/jira/browse/HADOOP-531
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: contrib/streaming
>    Affects Versions: 0.5.0
>            Reporter: Richard Kasperski
>
> There are many tasks where I need to have finer control over the ordering in the reduce than a sort on a single key provides. Most of these situations arise when a merge two sources of data and am attaching a single instance of one source to multiple instances of a second source. I know that I can read all the the records with a single key. It's possible that there might be many millions of these making memory demands that cannot be satisfied.

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