On 8/11/10 8:31 AM +0300, Peter Eisentraut wrote:
Thinking about SQL assertions (check constraints that are independent of
one particular table), do you think it would be reasonable to implement
those on top of constraint triggers? On creation you'd hook up a
trigger to each of the affected tables. And the trigger function runs
the respective check expression. Conceptually, this doesn't seem to be
very far away from foreign key constraints after all.
I thought the point of ASSERTIONs was that you could write a thing such as:
CREATE ASSERTION foo CHECK ((SELECT count(*) FROM tbl) = 4);
Enforcing that kind of constraints without true serializability seems
impractical.
Regards,
Marko Tiikkaja
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