Setting the "primary key" possible?

Question

We are trying to access an existing database using Kodo JDO. A part of
this database is old and not particularly well-designed.
Some tables does not have a primary key, eventhough they are entities that
need to be mapped to classes in our persistence layer. For the one table
we are looking at currently, we have changeed a unique index on a numeric
field to be the primary key, simply to make things work.
The table (x) is extremely simple:
id number
description varchar
We have defined the table as having application identity since the user
wants to control the values of the id column. In fact, he would like to be
able to update the value, as long as no other records in the system refers
to the record via a foreign key.
When updating the record we get a kodo.util.UserException saying that
changing the primary key is illegal for persisted objects.
This is of course reasonable seen from JDO, but in our old user interface,
it was possible to change this id as long as it was not referred to.
Is there any other way out of this than to add an "internalID" column with
datastore identify, make that the primary key and then have the id column
have a unique database constraint instead?? We would prefer to not change
the database schema, but are willing to if absolutely necessary.

Answer 1

Is there any other way out of this than to add an "internalID" column with
datastore identify, make that the primary key and then have the id column
have a unique database constraint instead?? We would prefer to not change
the database schema, but are willing to if absolutely necessary.Well, I guess you could do the following:
- Set some unmanaged field to the desired new pk value.
- Use a custom class mapping (probably extending
kodo.jdbc.meta.BaseClassMapping) to change the pk column on updates based on the
value of the unmanaged field.
It's not trivial, but it at least avoids schema changes. Note that it will only
work correctly if you have very short-lived PersistenceManagers, though. Once a
transaction that changes a pk value commits, the PM cache will be invalid; Kodo
will still think the object has its old pk value. You also couldn't use the
DataCache.