On Tue, 12 Nov 2002, [iso-8859-1] Cédric Dufour (Cogito Ergo Soft) wrote: > Hello, > > I am trying to figure out how to handle tuple deletion efficiently when ON > DELETE triggers and referential integrity are involved. The scenario is > about this one: > > I have a MASTER and a SLAVE table, the latter referencing the former through > a "FOREIGN KEY ... REFERENCES ... ON DELETE CASCADE" constraint. Besides, I > have a ON DELETE trigger on the SLAVE table which updates a field in the > MASTER table upon deletion. > > Now, there no need to update the MASTER table if the SLAVE table deletion > was actually fired by the FOREIGN KEY constraint. The ON DELETE trigger > updates a tuple in the MASTER table which will be deleted itself right > after. This can make the deletion of a MASTER table tuple very slow, if > there are a lot of related tuples in the SLAVE table. > > Is there any "by the book" way to handle this ?
Hmm, by the time that the on delete trigger runs after the foreign key action, I believe that the row in MASTER is already gone. Running a simple test in 7.3 seems to confirm this. Unfortunately it's still going to look for the row to update it. I can't think of a good way to tell if you're in an action that was caused by a foreign key rather than some other user trigger or rule or straight delete apart from some vague notions of really complicated workarounds which only partially help. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
