Group By step is not supported in a single threaded transformation engine

If you have a job that contains both a Pentaho MapReduce entry and a Reducer transformation with a Group by step, you may receive a Step 'Group by' of type 'GroupBy' is not Supported in a Single Threaded Transformation Engine error message. This error can occur if:

• An entire set of rows sharing the same grouping key are filtered from the transformation before the Group By step.

• The Reduce single threaded option in the Pentaho MapReduce entry's Reducer tab is selected.

To fix this issue, open the Pentaho MapReduce entry and deselect the Reduce single threaded option in the Reducer tab.