code: protected void setBigJoin(String[] masterLabels, String[] masterColumn,
                                String[] dataColumn, String masterSeparator, List<String> masterData)
                                        throws DataFormatException {
          if (masterColumn.length != dataColumn.length) {
              throw new DataFormatException("masterColumns and dataColumns lenght is miss match.");
          }
  
          this.conf.setInt(SimpleJob.READER_TYPE, SimpleJob.SOME_COLUMN_JOIN_READER);
          this.conf.setStrings(SimpleJob.MASTER_LABELS, masterLabels);
          this.conf.setStrings(SimpleJob.JOIN_MASTER_COLUMN, masterColumn);
          this.conf.setStrings(SimpleJob.JOIN_DATA_COLUMN, dataColumn);
          this.masterSeparator = masterSeparator;
          this.masterData = masterData;
      }
docs: to join the data that does not fit into memory.
  @param masterLabels label of master data
  @param masterColumn master column
  @param dataColumn data column
  @param masterSeparator separator
  @param masterData master data
  @throws DataFormatException