Hi Michael,
spec only says cascade which I think means associated entites are not
deleted even with Cascade.DELETE, but does not tell association itself
should be maintained or not - of course the association should be removed
for successful DELETE, but It's not clear that application should do it.
Also, do you have an idea regarding an UPDATE query which can remove
many-to-many association for DELETE query (1)?
Thanks,
-Wonseok
On 3/30/07, Michael Bouschen <Michael.Bouschen_at_sun.com> wrote:
>
> Hi Wonseok,
>
> I think a buld delete should not handled relationships. Here is what the
> spec says in chapter "4.10 Bulk Update and Delete Operations":
> A delete operation only applies to entities of the specified class and
> its subclasses. It does not cascade to related entities.
>
> Regards Michael
>
> > Hi Tom, Marina, Michael...
> >
> > While I'm investigating the issue 2744(bulk delete problem with
> > temporary table), I come to have a very curious question.
> >
> > Should bulk DELETE query handle relationships automatically or should
> > application do it manually by another query? It seems there is no
> > words about it in the specification.
> >
> > For example, if Department and Employee have one-to-many relationship,
> > and Employee and Project have many-to-many relationship like below.
> >
> > @Entity public class Department {
> > @Id Integer id;
> > String name;
> > @OneToMany(mappedBy="dept") Collection<Employee> employees;
> > }
> >
> > @Entity public class Employee {
> > @Id Integer id;
> > String name;
> > @ManyToOne Department dept;
> > @ManyToMany(mappedBy="members") Collection<Project> projects;
> > }
> >
> > @Entity public class Project {
> > @Id Integer id;
> > String name;
> > @ManyToMany Collection<Employee> members;
> > }
> >
> > (1) "DELETE FROM Project p WHERE p.name <http://p.name> = :name"
> > (there is many-to-many relationship bet. Project and Employee)
> >
> > Should this also remove many-to-many relation rows from relation table
> > automatically?
> >
> > TopLink is now doing this, generating DELETE SQLs of many-to-many
> > relations like below.
> >
> > ExpressionQueryMechanism:1165
> > // Add statements for ManyToMany and DirectCollection
> mappings
> > Vector deleteStatementsForMappings =
> > buildDeleteAllStatementsForMappings(selectCallForExist,
> > selectStatementForExist, tablesToIgnore == null);
> > if(!deleteStatementsForMappings.isEmpty()) {
> > if(getSQLStatement() != null) {
> > getSQLStatements().add(getSQLStatement());
> > setSQLStatement(null);
> > }
> > getSQLStatements().addAll(deleteStatementsForMappings);
> > }
> >
> > (2) "DELETE FROM Department d WHERE d.name <http://d.name> = :name"
> > (there is one-to-many relationship bet. Department and Employee)
> >
> > Similary, should this also remove one-to-many relations automatically?
> >
> > Toplink is *not* generating any SQLs to set relationship column of the
> > owner to NULL in this case, so foreign key constraint violation occurs!
> >
> > To avoid constraint violation, I should execute another query like
> > "UPDATE Employee e SET e.dept = NULL WHERE e.dept = :dept" before
> > DELETE query.
> >
> >
> > In sum, it seems that two cases are inconsistent and it's not clear
> > whether bulk DELETE query should handle relationship automatically.
> >
> > If it's not proper thing for provider to handle relationship like (1)
> > and application should always handle relationship for itself like I
> > did in (2), I could not figure out a query to update collection
> > association field to NULL for (1) like below.
> >
> > "UPDATE Project p SET p.members = NULL WHERE p.name <http://p.name> =
> > :name" -> p.members = NULL is error as JPQL only allows single valued
> > association field for update.
> >
> > I guess this issue seems something to be clearified in the spec.
> > Could anyone give me some explanation or opinion about this?
> >
> > Thanks,
> > -Wonseok
> >
>