Martijn van Oosterhout <kleptog@xxxxxxxxx> writes: > On Tue, Jun 24, 2008 at 10:28:00AM -0500, Michael Shulman wrote: >> My question was, what else *can* you do with a rule that you *can't* >> do with a trigger? Are rules only a way to speed up things that could >> also be done with triggers? > Well, views for one. To expand on that: it's pretty hard to see how update or delete triggers on a view would work. Insert is easy, because if left to its own devices the system would in fact try to insert a tuple into the view relation, and that action could fire a trigger which could redirect the insertion someplace else. But updates and deletes require a pre-existing target tuple, and there just aren't any of those in a view relation. (Another way to say it is that update/delete require a CTID column, which a view hasn't got.) So view update/delete appear to require a transformational-rule kind of approach instead of an actions-on-physical-tuples kind of approach. If you've got a better idea we're all ears ... regards, tom lane
