Newbie question: SQL operations automatically reordered so a DELETE comes first?

Question

Hi -
I have two objects that are related to each other by a one-to-many relationship. In my test case
there's a single A object that is related to a single B object. I want to sever the relationship
between the two objects (a SQL UPDATE behind the scenes) and then delete one of them (a SQL
DELETE).
What I'm seeing is that the SQL DELETE is issued before the SQL UPDATE. I'm running Kodo 2.3.2.
Here's the Java code:
// sever A's relationship to B, which issues a SQL UPDATE
objectA.getBs().remove(objectB);
// sever B's relationship to A
objectB.setA(null);
m_pm.makePersistent(objectB);
// delete object A, which issues a SQL DELETE
m_pm.deletePersistent(objectA);
If this Java code is in a single transaction, the DELETE occurs before the UPDATE and fails because
of a foreign key constraint. If the deletePersistent call is moved to a separate transaction, all
work is completely successfully.
Is this behavior by design? Did I miscode something?
Thanks in advance,
Les

Answer 1

Thanks Abe. I actually thought I was ordering the operations but I can see now that I wasn't
thinking about the order that the objects joined the transaction.
And thanks for posting a quick reply; that's a big help.
Les
"Abe White" <[email protected]> wrote in message news:aoi7p0$euu$[email protected]..
Kodo will performs database operations on a per-object basis, and orders each
object's database operations according to when that object joined the
transaction.
In your case, objectA is joining the transaction as soon as you call
objectA.getObjectBs ().remove (objectB);
So even though the explicit deletion of objectA doesn't happen until later,
Kodo places it at the point where objectA joined the transaction. To work
around this, just change your code:
objectB.setObjectA (null);
objectA.getObjectBs ().remove (objectB);
pm.deletePersistent (objectA);
Note that internal builds of Kodo have support for automatic foreign key
analysis and INSERT/UPDATE/DELETE ordering, but the feature probably won't
be debuted publicly for a couple of months.