Hi Andrus, On Jun 7, 2007, at 11:38 PM, Andrus Adamchik wrote:
On Jun 8, 2007, at 7:01 AM, Craig L Russell wrote:Just FYI, when JDO reads data from tables without PK, it internally creates a unique id, similar to a generated PK, for the objects that it reads and these ids are discarded when no longer needed. The fact that the mapping is for tables without PK is known by the code that creates the temporary ids.CraigHi Craig,I can probably implement this in Cayenne in about 30 minutes, as Cayenne has a notion of "temporary id" (normally used for new uncommitted objects). The problem of course is uniquing. So say if a DB row is fetched from a table via a query, resulting in object A, and then later the same row is navigated to via a relationship from another object, resulting in a second object B, distinct from A. This breaks the fundamental assumption about object identity. So we chose not to go this way.
If you can navigate to a single A via a relationship, to me that implies that you have some unique constraint by which a single A is associated with another row. And if you have a unique constraint, then you can use that instead of a primary key.
Craig
Andrus
Craig Russell Architect, Sun Java Enterprise System http://java.sun.com/products/jdo 408 276-5638 mailto:[EMAIL PROTECTED] P.S. A good JDO? O, Gasp!
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