Can I specify EntityTransaction transaction order? - constraints

Question

We've having a problem doing an insert into two tables in a single transaction in our H2 database using EclipseLink JPA.
The database schema looks something like ...
Table A {...,
IP_ADDRESS Varchar2( 15 ) not null
}
Table B {...,
IP_ADDRESS Varchar2( 15 ) not null,
constraint MY_FK foreign key (IP_ADDRESS) references A
}
The problem we are having is that the foreign key constraint on B is making the transaction fail.
We're doing this:
entityManager.getTransaction().begin();
entityManager.merge ( Save to A transaction );
entityManager.merge ( Save to B transaction );
entityManager.getTransaction().commit();
It looks like JPA is trying to do the save to B first and failing.
Or perhaps it is checking the constraint on B first?
At any rate, what we'd like to do ideally is something like what I recall from many years ago, using PL/SQL on oracle:
BEGIN
Do the insert on A;
Do the insert on B;
commit;
End;
I don't think Oracle looked at the constraint until the transaction was complete. Or allowed it complete because the uncommitted version of the transaction did not violate the constraint.
Any thoughts? I looked at the documentation and have not found anything helpful yet.
Thanks

Answer 1

I believe I have found the problem, although I would love a confirmation from somehow who knows JPA better than I do.
The issue here was that there was no definition of the foreign key constraint in the entity classes representing the two tables.
As a result, the EntityManager knew nothing about the relationship between the two tables and picked an arbitrary insert order.
The transaction then failed because JPA tried to insert the table B row before the the row for table A.
I fixed this by adding a #ManyToOne relationship in table B, and a #OneToMany relationship table A. I set the fetch type to lazy as the relationship definition as there is no need to use any fetch results.
In the Table A entity class:
// bi-directional one-to-many association to PositionHostPermission
#OneToMany( mappedBy = "the a entity", fetch=FetchType.LAZY )
private Set<B> bInstances;
In the Table B entity class:
//bi-directional many-to-one association to ipAddress
#ManyToOne( fetch= FetchType.LAZY )
#JoinColumn(name="IP_ADDRESS",insertable=false, updatable=false )
private A aTableInstance;