# Mapper tab

![Pentaho MapReduce Mapper tab](/files/Vm9YuRjeZ9hjKBfx0WAm)

The following table describes the options for defining a mapper transformation, which is required by this entry:

| Option               | Definition                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| -------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Transformation**   | <p>Specify the transformation that will perform the mapping functions for this job by entering its path or clicking <strong>Browse</strong>.</p><p>If you select a transformation that has the same root path as the current transformation, the variable\*\*${Internal.Entry.Current.Directory}\*\* will automatically be inserted in place of the common root path. For example, if the current transformation's path is <code>/home/admin/transformation.ktr</code> and you select a transformation in the folder <code>/home/admin/path/sub.ktr</code> than the path will automatically be converted to <code>**${Internal.Entry.Current.Directory}**/path/sub.ktr</code>.</p><p>If you are working with a repository, specify the name of the transformation in your repository. If you are not working with a repository, specify the XML file name of the transformation on your system.</p><p><strong>Note:</strong> Transformations previously specified by reference are automatically converted to be specified by name within the Pentaho Repository.</p> |
| **Input step name**  | Specify the name of the step that receives mapping data from Hadoop. It must be a MapReduce Input step.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| **Output step name** | Specify the name of the step that passes mapping output back to Hadoop. It must be a MapReduce Output step.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |


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