Abe,
Check the below example
Owner owner = new Owner("Ted");
owner.add(new Dog("one"));
owner.add(new Dog("two"));
TABLE OWNER
ID NAME
1 Ted
TABLE OWNER_DOG
OWNER_ID NAME
1 one
1 two
If owner_id is primary key and nothing else, we will not be able to store more
than one instance of Dog for each owner. Thus, we need a new column to be part
of the primary key.
TABLE OWNER_DOG
OWNER_ID UNIQUENESS_ID NAME
1 1 one
1 2 two
Adding one more column will help if we dont have duplicates, but with duplicates
we need 3 columns.
Example
Owner owner = new Owner("Ted");
Dog one = new Dog("one");
Dog two = new Dog("two");
owner.add(one);
owner.add(one);
owner.add(two);
The only way I can think it to work is with the following schema
TABLE OWNER
ID NAME
1 Ted
TABLE OWNER_DOG
OWNER_ID UNIQUENESS_ID EMBEDDED_ID NAME
1 1 1 one
1 2 1 one
1 3 2 two
Quoting Abe White <[EMAIL PROTECTED]>:
> > The issue came up with the TCK where we were trying to get JPOX to
> > recognize that an embedded PersistenceCapable in a join table can
> > have a unique identifying field. In the case of datastore identity,
> > this doesn't work because there is no primary key field in the
> > PersistenceCapable.
> >
> > <proposed 18.14>
> > A portable mapping for arrays, collections, and maps will include a
> > primary key on the join table.
> > </proposed 18.14>
>
> Why? I don't understand this at all. "Datastore identity" is
> meaningless in this context, as embedded objects have no identity
> according to the spec.
>
