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From "Durchholz, Joachim" <>
Subject RE: Foreign keys whe migrating
Date Mon, 21 Nov 2011 09:37:06 GMT
> Oracle and MS-SQL do not suffer from this limitation, but I've done no testing to verify

For Oracle, the constraint needs to be configured for "deferrable" checking (available since
8i, don't know how well it works today). That postpones constraint checks to commit time,
and I think it is not the default.
In other words, in a legacy schema, Oracle's constraint checking will be on a per-DML-statement
SET CONSTRAINTS ALL DEFERRED will make Oracle postpone all constraint checking to the next
commit (the Oracle docs claim this is ANSI SQL92 syntax and semantics).
Oracle in general is bad at reporting what data exactly caused some constraint violation;
deferring checks to commit time is going to make that worse if at all possible.

Just enumerating the issues.
I sure would like to see deferred checking in Cayenne. I have absolutely no idea whether it's
worth the challenges though.

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