code: protected void populateColumnSchema(ArrayList<ColumnInfo> columns) {
          columns.add(new ColumnInfo("TIMESTAMP", VoltType.BIGINT));
          columns.add(new ColumnInfo(VoltSystemProcedure.CNAME_HOST_ID,
                                     VoltSystemProcedure.CTYPE_ID));
          columns.add(new ColumnInfo("HOSTNAME", VoltType.STRING));
      }
docs: Called from the constructor to generate the column schema at run time.
  Derived classes need to override this method in order to specify the
  columns they will be adding. The first line must always be a call the
  superclasses version of populateColumnSchema
  in order to ensure the columns are add to the list in the right order.
  @param columns Output list for the column schema.