@Override
  public void transform(Row row, PointCollector collector) throws Exception {
    String[] splitResult = row.getString(0).split(regex);
    if (index == -1) {
      collector.putInt(row.getTime(), splitResult.length);
    } else {
      if (index < splitResult.length) {
        collector.putString(row.getTime(), splitResult[index]);
      }
    }
  }
This function splits string from an input series according to given regex.
library-udf/src/main/java/org/apache/iotdb/library/string/UDTFRegexSplit.java