[jira] Updated: (HADOOP-3684) The data_join should allow the user to implement a customer cloning function

["Robert Chansler (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-3684?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Chansler updated HADOOP-3684:
------------------------------------

    Release Note: Allowed user to overwrite clone function in a subclass of TaggedMapOutput class.  (was: make it possible for the user to overwrite clone function in a subclass of TaggedMapOutput class)

> The data_join should allow the user to implement a customer cloning function
> ----------------------------------------------------------------------------
>
>                 Key: HADOOP-3684
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3684
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Runping Qi
>            Assignee: Runping Qi
>             Fix For: 0.19.0
>
>         Attachments: H-3684.txt
>
>
> Currently, the framework uses serialization/deserialization to clone the values passed to the resuce function.
> This amounts to a very heavy weight deep copy of the value objects.
> That is way too expensive. Although that may be a generic way to work for all possible value classes, thus good as a default way,
> the framework should allow the user to implemet an application specific yet efficient cloning function.
>  

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