@Override
  public PageOutput open(
      TaskSource taskSource,
      final Schema inputSchema,
      final Schema outputSchema,
      final PageOutput output) {
    final PluginTask task = taskSource.loadTask(PluginTask.class);

    // create jsonColumns/baseColumn
    final List<Column> outputColumns = outputSchema.getColumns();
    final List<Column> inputColumns = inputSchema.getColumns();

    Map<String, Column> inputColumnMap = Maps.newHashMap();
    final List<Column> jsonColumns = new ArrayList<>();
    for (Column column : outputColumns) {
      if (!inputColumns.contains(column)) {
        jsonColumns.add(column);
      } else {
        inputColumnMap.put(column.getName(), column);
      }
    }

    final Column baseColumn = inputColumnMap.get(task.getBaseColumn().getName());

    // create timestampParserMap
    final HashMap<String, TimestampParser> timestampParserMap = Maps.newHashMap();
    for (ColumnConfig jsonColumnConfig : task.getJsonColumns()) {
      if (Types.TIMESTAMP.equals(jsonColumnConfig.getType())) {
        String format = jsonColumnConfig.getOption().get(String.class, "format");
        DateTimeZone timezone = DateTimeZone.forID(task.getTimeZone());
        TimestampParser parser = new TimestampParser(task.getJRuby(), format, timezone);
        timestampParserMap.put(task.getJoinedColumnsPrefix() + jsonColumnConfig.getName(), parser);
      }
    }

    // get jsonTable
    final HashMap<String, HashMap<String, String>> jsonTable = task.getJsonTable();

    return new LeftOuterJoinJsonTableFilterFilteredPageOutput(
        inputSchema, outputSchema, baseColumn, jsonTable, jsonColumns, timestampParserMap, output);
  }