Greg Stark <stark@mit.edu> writes:
> I dislike both of the explanations above which don't actually explain
> why people shouldn't use rules (Josh does say they're tricky which is
> a start). Just telling people we hate parts of the system doesn't
> really come off well and leaves them wondering why.
Agreed. I think that by far the most common problem people hit with
rules has to do with unexpected multiple evaluations of volatile
functions (eg nextval). If we're going to put in some warning text
I think it would be smart to explain that and maybe even show an
example. It'd be easy enough to generate an example involving,
say, a rule that's meant to log rows that are inserted.
regards, tom lane