From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
---|---|
To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
Cc: | alexk(at)commandprompt(dot)com, pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: the '::' cast doesn't work in the FROM clause |
Date: | 2011-08-29 19:20:08 |
Message-ID: | CAHyXU0wyZPjR1iC7yKzTn8t1ZD4vXMPQW8PwdbxFeDH+aCm9uw@mail.gmail.com |
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Lists: | pgsql-bugs |
On Mon, Aug 29, 2011 at 9:00 AM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>
>> yeah, that's the correct way, but why does this work?
>> select val from random() as val;
>
> If you look at the PostgreSQL reference docs for the SELECT
> statement, a from_item can be a SELECT statement in parentheses or a
> function call (among other things). It cannot be an arbitrary
> expression containing operators (like ::).
right -- duh. I knew that...the canonical case for this is the
definition of pg_locks view. I've just never seen it used for a
regular scalar function. The whole thing is pretty peculiar IMO (but
useful occasionally).
merlin
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