code: private void setAggregationColInInterpreter(EntityMetadata m, CouchDBQueryInterpreter interpreter, Expression exp)
      {
          if (StateFieldPathExpression.class.isAssignableFrom(exp.getClass()))
          {
              Map<String, Object> map = KunderaQueryUtils.setFieldClazzAndColumnFamily(exp, m, kunderaMetadata);
              interpreter.setAggregationColumn((String) map.get(Constants.COL_NAME));
          }
      }
docs: Sets the aggregation col in interpreter.
  
  @param m
  the m
  @param interpreter
  the interpreter
  @param exp
  the exp