[ 
http://issues.apache.org/jira/browse/HADOOP-451?page=comments#action_12427953 ] 
            
Doug Cutting commented on HADOOP-451:
-------------------------------------

> You will probably need to add a "setSplitClass" and "getSplitClass" to 
> JobConf 

The InputFormat is a Split factory, no?  Who else would need to create Splits?

Splits are passed in RPCs, and the RPC mechanism supports polymorphism.  Splits 
are not written to files, so I see no reason to declare a fixed class per job.  
Am I missing something?

> Add a Split interface
> ---------------------
>
>                 Key: HADOOP-451
>                 URL: http://issues.apache.org/jira/browse/HADOOP-451
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Doug Cutting
>             Fix For: 0.6.0
>
>
> The InputFormat interface has a method:
> FileSplit[] getSplits();
> This should change to:
> Split[] getSplits();
> The Split interface would look like:
> public interface Split extends Writable {
>   /** Returns a list of hosts that contain this split.
>        This is only used to optimize task placement, so this may be empty. */
>   String[] getLocations(FileSystem fs);
>   /** The relative, estimated cost of operating on this.  Typically the size 
> of the data in the split.
>        Used to prioritize tasks in a job (high-cost tasks are run first).  */
>    long getCost();
> }

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