Ed Loehr wrote:
> At least in 6.5.2, you can definitely implement referential integrity
> (RI) via pl/pgsql. As someone noted earlier, RI is to be released in
> 7.0, but I suspect it will take a subsequent release or two to
> stabilize before it's fit for consumption by the more conservative
> reliability-focused users among us...
I hope that this isn't true.
First, because FOREIGN KEY is implemented as builtin triggers written in C. BETA should turn out most of the
bugs, which could still be in it.
Second, RI cannot get implemented reliable with regular triggers. You can easily violate the
semantics with concurrently running transactions. Have first transaction inserting a reference, the trigger
checksfor key existence and finds it. Now second transaction deletes the key, and an eventually existing ON
DELETECASCADE trigger fired on that wouldn't find the reference, because it isn't committed yet. Second
transactioncommits, what finally removes the key. Now first transaction commits, making the reference visible, but
referencinga non existing key - inconsistency.
So anyone who needs referential integrity is asked to stress the code as far as he can, at least during BETA.
Jan
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#========================================= wieck@debis.com (Jan Wieck) #
