jan pfaler <jan_pfaler(at)yahoo(dot)se> writes:
> The rule-system seems to evaluate a functional value
> of a column anew. Please confim if this is a
> documented/intentional behaviour of the rule system?
Yes.
> The order of evaluation of the expresion(s) within
> original statemant and rule differ between "on insert"
> and "on update" rules.
Order of evaluation is never guaranteed.
Generally it's better to use triggers for the sort of problem you show
here.
regards, tom lane