[ 
http://issues.apache.org/jira/browse/HADOOP-433?page=comments#action_12426763 ] 
            
Owen O'Malley commented on HADOOP-433:
--------------------------------------

This is largely addressed by the extensions I put into the JobConf task 
localization code. Look at MapTask.localizeConfiguration.

In particular, each Mapper has available to it:
map.input.file
map.input.start
map.input.length

For application writers that don't want to read the Hadoop code, I've put the 
list of attributes in:
http://wiki.apache.org/lucene-hadoop/TaskExecutionEnvironment

This will let you get an equivalent RecordReader even if it is not the same 
object. Will that address your problem?

> Better access to the RecordReader
> ---------------------------------
>
>                 Key: HADOOP-433
>                 URL: http://issues.apache.org/jira/browse/HADOOP-433
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.5.0
>            Reporter: Benjamin Reed
>            Priority: Minor
>
> The record reader has access to the FileSplit which can in turn have 
> information that is useful to the Mapper. For example, Map processing may 
> vary according to file name or attributes associated with a file. 
> Unfortunately, even using a MapRunner you only have access to the progress 
> wrapper of the RecordReader. To get access to the real record reader I had to 
> use a thread local variable which I set in RecordReader.getNext(). It would 
> be much nicer if you could get a reference to the real RecordReader from the 
> RecordReader passed to MapRunner.

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