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
>