级联删除不起作用（NHibernate）

Question

I have master-detail table and I want to have casade delete-update that means when i delete record from Customer it should be automatically deleted related Orders to that Customer.

Here is definition of tables:

Customer table:

  <class name = "Customer">

    <id name="ID" column="ID" type="string">
      <generator class="assigned" />
    </id>

    <property name = "FirstName"/>
    <property name = "LastName"/>
    <property name = "AverageRating"/>
    <property name = "Points"/>
    <property name = "HasGoldStatus"/>
    <property name = "MemberSince" type = "DateTime"/>

    <bag name="Orders" inverse="true" cascade="all-delete-orphan" >
      <key column="CustomerId"/>
      <one-to-many class="Orders"/>
    </bag>   
    
  </class>
</hibernate-mapping>

Orders table:

<?xml version = "1.0" encoding = "utf-8" ?>

<hibernate-mapping xmlns = "urn:nhibernate-mapping-2.2"
   assembly = "NHibernate_example_1" namespace = "NHibernate_example_1.Models">

  <class name = "Orders">        
    <id name = "ID">
      <generator class = "native"/>
    </id>

    <property name = "Ordered"/>
    <property name = "Shipped"/>

    <many-to-one name="Customer" column="CustomerId" class="Customer" />
  </class>

</hibernate-mapping>

But after creating tables FK has this property:

CONSTRAINT FK_E4664020 FOREIGN KEY ( CustomerId ) REFERENCES customer ( ID ) ON UPDATE RESTRICT ON DELETE RESTRICT

How to set ON UPDATE CASADE ON DELETE CASCADE ?

I'm using MySQL and nHibernate 5.3.0