public void clear() {
    udfInformationMap.get(Model.TREE).clear();
    udfInformationMap.get(Model.TABLE).clear();
    functionToClassMap.get(Model.TREE).clear();
    functionToClassMap.get(Model.TABLE).clear();
  }
maintain a map for creating instance, model -> functionName -> class
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/udf/UDFTable.java