Hello,

I'm using Hiberate version 3.3.1 and trying to write a very simple one to many mapping where deletes are performed efficiently. I've got a number of mappings and am happy with Hibernate for inserting/selecting/etc., but I'm looking at how to efficiently delete relationship, and failing to find a good example.

I have two objects, Application and Event. Application has a set of Events (so a one to many relationship).

Here are the relevant mappings:

<hibernate-mapping>
<class name="Application">
<cache usage="read-write"/>
<id name="id" column="applicationId">
<generator class="native"/>
</id>

<set name="events" inverse="true"
cascade="all,delete-orphan" lazy="extra">
<key column="applicationId" />
<one-to-many class="Event" />
</set>
</class>
</hibernate>

<hibernate-mapping>
<class name="Event" polymorphism="implicit">
<id name="id" column="eventId">
<generator class="native"/>
</id>
<many-to-one name="application"
column="applicationId"
not-null="true"/>
</class>
</hibernate>

This relationship works perfectly correct for adding/updating - I can add events to the set in Application, call session.persist(application) and everything is updated as I would expect. However the delete is very inefficient. If I delete an application then hibernate deletes each event separately;

Hiberate: delete from Event where eventId=?
etc.

What I'd like it to do is:

delete from Event where applicationId=?

This seems a fairly basic requirement so I apologise for clearly missing the documentation, but could someone tell me how it's done?

Thanks,


J

I see the solution:

<set name="events" inverse="true"
cascade="all,delete-orphan" lazy="extra">
<key column="applicationId" />
<one-to-many class="Event" />
</set>

should be:

<set name="events" inverse="true"
cascade="all,delete-orphan" lazy="extra">
<key column="applicationId" on-delete="cascade" />
<one-to-many class="Event" />
</set>

I would have assumed a cascade delete would be the default behaviour!

I am also running into the same problem where multiple deletes are getting executed

As suggested by you If we put this attribute on-delete = 'cascade' that means we are setting the cascade at the Database level and Hibernate is not executing the delete statements.

Is there any way to tell Hibernate to delete the children at one shot?

delete children where parent_id = ?