@Override
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null || getClass() != obj.getClass()) {
      return false;
    }
    FunctionViewExpression that = (FunctionViewExpression) obj;
    return functionName.equals(that.functionName)
        && functionAttributesKeyValueList.equals(that.functionAttributesKeyValueList)
        && expressions.equals(that.expressions);
  }
example: select udf(a, b, udf(c)) from root.sg.d;

<p>3 expressions [root.sg.d.a, root.sg.d.b, udf(root.sg.d.c)] will be in this field.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/schema/view/viewExpression/multi/FunctionViewExpression.java