On Thu, 2008-05-08 at 14:56 +0200, Peter Eisentraut wrote:
> Am Donnerstag, 8. Mai 2008 schrieb Simon Riggs:
> >  CREATE RULE somename AS ON INSERT TO x WHERE where-clause DO INSERT ...
> >
> > which seems straightforward, no?
> Double evaluation is the key word.  The conclusion was more or less that you 
> can't implement check constraints using the rules system.  You need to check 
> them in the executor.

That makes sense. I can't see how we would make LOCAL CHECK CONSTRAINTs
work with rules anyhow.

So that means WITH CHECK CONSTRAINT is going to end up executed in a
similar place to constraint evaluation on underlying tables.

That leaves me in a difficult position with MERGE though. MERGE does
something similar with conditional-WHEN clause evaluation, plus
transformation of the sub-statements is only sensible when we have
updatable views. :-(

  Simon Riggs
  2ndQuadrant  http://www.2ndQuadrant.com

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