Message-ID: <4118D14C.EA49F8CB@rodos.fzk.de>
Date: Tue, 10 Aug 2004 15:44:44 +0200
From: Christoph Haller <ch@rodos.fzk.de>
MIME-Version: 1.0
To: Lars Erik Thorsplass <thorsplass@gmail.com>,
	pgsql-sql@postgresql.org
Subject: Re: Stored procedures and "pseudo" fields
References: <7eeb33a040720034319e036c6@mail.gmail.com>
	<1090338306.709.25.camel@localhost.localdomain>
	<7eeb33a040720150320bf5eed@mail.gmail.com>
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Lars Erik Thorsplass wrote:

> On Tue, 20 Jul 2004 09:45:06 -0600, Scott Marlowe <smarlowe@qwest.net> wrote:
> > > Kinda like this:
> > >
> > > SELECT *, acl_check( objects.obid, <user_id> ) AS mode FROM objects
> > > WHERE mode > 0;
> >
> > Here's the problem. In order to do the select, the query first needs to
> > run the where clause.  I.e.:
> >
> > select a as test from table where a > 50;
> >
> > works, but
> >
> > select a as test from table where test > 50;
> >
> > fails.  The reason is that when the where clause fires first, there IS
> > no test yet, as it hasn't been materialized.  what you need to do is:
> >
> > select custom_function(a,b) from table where custom_function(a,b) > 0;
> >
> >
>
> Thanks for clearing that up. I just hoped there was some magic I could
> sprinkle on my query to get away from the extra overhead of running
> the procedure twice :)
>
> Best regards..
>
> L.E.Thorsplass
>

Pretty late, I know, but just for the record, AFAICS there is this magic as
SELECT * FROM (
SELECT *, acl_check( objects.obid, <user_id> ) AS mode FROM objects
) AS foo WHERE mode > 0;

Regards, Christoph