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DB2 triggers for primary keys

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ambermoon

Post subject: DB2 triggers for primary keys

Posted: Tue May 04, 2004 5:30 am

Newbie

Joined: Mon Apr 26, 2004 5:17 pm
Posts: 13

Hi there,

My DB2/390 DBA forces me to use triggers for generating unique primary keys. Like this one:

Code:

CREATE TRIGGER ABS.ABSINSERTORDER NO CASCADE BEFORE INSERT ON ABS.ABSORDER 
REFERENCING NEW AS new FOR EACH ROW MODE DB2SQL 
BEGIN ATOMIC SET new.ORDERID = (SELECT COALESCE(MAX(ORDERID) + 1, 0) FROM ABS.ABSORDER); SET new.ORDERAMOUNT = COALESCE(new.DELIVERYPRICE, 0); 
END

What would be the hibernate mapping and the handling for such a class/table?

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michael

Post subject:

Posted: Tue May 04, 2004 5:39 am

Hibernate Team

Joined: Tue Sep 09, 2003 2:10 pm
Posts: 3246
Location: Passau, Germany

You will either have to create your own generator, or I think you could use asigned and do a session.refresh(object) every time after saving.

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ambermoon

Post subject:

Posted: Tue May 04, 2004 7:00 am

Newbie

Joined: Mon Apr 26, 2004 5:17 pm
Posts: 13

Ah ok. That means that assign doesen't checks if I have "null" in my primary key on my object?

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gavin

Post subject:

Posted: Tue May 04, 2004 7:14 am

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

It is worse than that - you have to figure out some way to retrieve the value generated by the trigger. You can tell your DBA to solve this problem for you, and if (s)he cannot, you have a damn good reason to tell your DBA that this is a Bad Way to generate primary keys.

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ambermoon

Post subject:

Posted: Tue May 04, 2004 9:21 am

Newbie

Joined: Mon Apr 26, 2004 5:17 pm
Posts: 13

That was right. I could convince him to use a identity generator on the db2/390.

But now when my application crashes during a session. It sometimes locks the table forever....

Are there any options to prevent such errors? Like isolation level?

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