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From "Reece Garrett (JIRA)" <>
Subject [jira] Commented: (OPENJPA-235) SQL reordering to avoid non-nullable foreign key constraint violations
Date Thu, 24 May 2007 21:12:16 GMT


Reece Garrett commented on OPENJPA-235:

I am just about done revising my patch but I do not have access to the TCK and can not sign
the NDA  because I work for a government agency which will not allow it. All the test cases
I can run (mvn test) pass but that's not saying much because they passed the first time. As
I said, I have caught a few cases that I did not think of the first time and am hopeful that
they were the source of the TCK failures but can not be sure.  Also, the algorithm is now
iterative instead of recursive,  does almost no collection copying, and orders rows based
purely on dependencies instead of lumping all inserts first followed by updates and then deletes.
I decided not to include support for ordering unique keys until I get foreign key ordering
resolved (although I'm fairly certain my idea for unique keys will work well.

I'm at a loss as to how to proceed from here. I'll have a new patch ready soon but since I
can not run the TCK tests myself I don't feel comfortable resubmitting it and potentially
taking up more of your development time tracking down bugs I've introduced. What should I
do with my new patch? 

> SQL reordering to avoid non-nullable foreign key constraint violations
> ----------------------------------------------------------------------
>                 Key: OPENJPA-235
>                 URL:
>             Project: OpenJPA
>          Issue Type: Improvement
>          Components: kernel
>            Reporter: Reece Garrett
>         Assigned To: Patrick Linskey
>             Fix For: 0.9.8
>         Attachments: sqlreorder.patch
> OpenJPA does not do any SQL statement re-ordering in order to resolve foreign key constraints.
Instead, objects are always inserted in the order in which the user persists the instances.
 When you persist in an order that would violate foreign key constraints, OpenJPA attempts
to insert null and then update the foreign key value in a separate statement. If you use non-nullable
constraints, though, you must persist your objects in the correct order.
> This improvement re-orders SQL statements as follows:
> 1. First, all insert statements execute. Inserts which have foreign keys with non-nullable
constraints execute AFTER the foreign keys which they depend on have been inserted since no
deferred update is possible.
> 2. Next, all update statements execute. No reordering is necessary.
> 3.  Finally, all delete statements execute. Like inserts, deletes execute in an order
which does not violate non-nullable foreign key constraints.
> If a circular foreign key reference is found during the re-ordering process then re-ordering
halts and the remaining unordered statements are left as is. There is nothing that can be
done about the circular reference (other than fixing the schema) and the resulting SQL statements
will not succeed.
> The net effect is that users do not need to worry about the persistence order of their
objects regardless of non-nullable foreign key constraints. The only class modified was org.apache.openjpa.jdbc.kernel.OperationOrderUpdateManager.
I have included a patch which includes my modifications to OperationOrderUpdateManager and
test cases. The test cases I have provided fail on the current trunk but pass with my modifications.
I have also verified that I did not break anything by using maven to run all test cases with
my modifications in place.

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