I've been trying to resolve a problem using MySQL where an expected cascade delete from parent to children has not been happening. XDoclet is used to generate the mapping, from which this is a relevant excerpt (from the mapping for the parent, AdminLevel):

<set name="adminUsers"
lazy="false"
inverse="true"
cascade="all-delete-orphan"
sort="unsorted">
<key column="admin_level_id"></key>
<one-to-many class="sailingnetworks.om.AdminUser" />
</set>

hbm2ddl is used to generate the schema. Now the odd, and surely significant, thing is that the schema generated has no mention of cascades. The relevant line is this:

alter table admin_user add index FK29045ABB968E6EA6 (admin_level_id), add constraint FK29045ABB968E6EA6 foreign key (admin_level_id) references admin_level (id);

When run, we get a foreign key constraint error instead of a cascade. However, manually adding 'on cascade delete' to the end of the above 'alter table...' line makes it all work as planned. Does hbm2ddl not correctly generate the 'on cascade xxx' code?

Hibernate 2.1.6, MySQL 4.0.22 on Mandrake Linux 10.1.

Correction: Hibernate 2.1.4

Further correction: an upgrade to 2.1.7c makes no difference.

This is STILL not working in 3.2.x . . . I have found numerous posts on the web pertaining to this problem, dating back to 2004, but it appears the issue has still not been addressed.

Here are some of the issues logged:

http://opensource.atlassian.com/projects/hibernate/browse/HHH-2263
http://opensource.atlassian.com/projects/hibernate/browse/ANN-598
http://opensource.atlassian.com/projects/hibernate/browse/HB-1094

The interesting thing here . . . notice on HB-1094, Gavin King mentions that this has been added to the Hibernate 3 branch. If you read Section 5.1.19 of the Hibernate Docs, it states . . .



This would imply that by simply placing on-delete="cascade" to a key on, say, a one-to-many set, this should add ON DELETE CASCADE to the DDL generated by way of HBM2DDL . . . but it doesn't!!!

Here is a one-to-many I have set up, where I want ON CASCADE DELETE to apply to the foreign key, but it is not being added to the DDL:



if I take the on-delete="cascade" off and add cascading on the set, I get individual delete statements, which also results in ALL of the objects being loaded(their children and their children, and so on) and subsequently deleted(which takes forever and requires a lot of memory).

Is there a way to get ON CASCADE DELETE added to HBM2DDL generated DDL or no?

It appears what fixed my problem is the hibernate.dialect property. This needs to be set at a value of org.hibernate.dialect.MySQLInnoDBDialect rather than org.hibernate.dialect.MySQLDialect

This works for one-to-many deletes, but not for many-to-many. There still does not appear to be a good way to perform a many-to-many delete, which cascades from the left side table, through to the association table, removing the association table's rows, then removing the left side table's rows in this case. The only way I have seen where this is possible is removing the object from the parent's collection in Java code, which I don't want to do. I would hope there is a way to simply call session.delete(parent) and have the cascading propagate down to all levels.