Re: Rules/Trigges Trade-offs

Josh Berkus wrote:
>
> Bruce,
>
> > > 1) Rules can't use indexes to do their processing, so Rules which query
> large
> > > secondary tables can be a bad idea (maybe this has changed?)
> >
> > I don't think this is true. Rewrite is before optimizer so it should be
> > optimized just the same.
>
> I was speaking if the Rule has to do a lookup on a 2nd table in the course of
> its processing; it used to be that such a lookup could not use indexes
> because Rules are pre-optimizer. This could have changed since 7.1, though.

As I remember, the RULE is processed just like an ordinary query. I
wasn't aware it was looking up anything.

> > > 3) There are no AFTER Rules, making, for example, a rule with a table
> check on
> > > the new data impractical, so you'd want to use Triggers or Constraints
> >
> > We have changed ordering in 7.3 where I think INSERT rules are _after_
> > the insert.
>
> How would that work? What if I want to reject the insert?

Uh, good question. I can't remember now what we re-ordered in 7.3, but
I thought it had to do with rules.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073