docs: 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));
      }