"Gerhard Pfeiffer" <gp(at)bnbt(dot)de> writes:
> It shouldn't show me this error, because the update invoked by the rule
> doesn't fulfill the condition (new.ent_udate=old.ent_udate).
Rules are macros rewritten at planning time, not at execution time,
so you cannot escape the rewrite cycle with an execution-time condition.
You will probably have better luck doing what you want to do with
a trigger.
regards, tom lane