| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Cc: | pgsql-patches(at)postgresql(dot)org, Bernd Helmle <mailings(at)oopsware(dot)de> |
| Subject: | Re: Updatable views |
| Date: | 2008-05-08 13:42:50 |
| Message-ID: | 1210254170.4268.365.camel@ebony.site |
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| Lists: | pgsql-hackers pgsql-patches |
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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