On Fri, Aug 28, 2009 at 06:12:30PM +0300, Marko Tiikkaja wrote:
> Hi everyone,
>
> Today I needed a feature like $subject. The use case was: UPDATE
> foo SET bar = bar + 1 WHERE id=$1, but I wanted to only do it when
> bar was 0. In order to give the user an informative error message,
> I also needed to distinguish the two cases: a row with id = $1
> doesn't exist, and bar was 0, so I couldn't put bar != 0 into the
> WHERE clause. This time I got around it by using RETURNING bar and
> checking that it was 1 on the client side, but I can come up with
> other cases where you can't do that.
>
> Comments?
We talked about this briefly in IRC last night, and since that's not
recorded, I'd like to mention a few things here:
* OLD is already a reserved word. We could use it without fear of a badly named database object.
* Having access to both the old and new row could make debugging complex UPDATE queries much easier.
* There's some interesting use cases if the UPDATE...RETURNING can also be used as a subquery. Auditing would be one.
Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
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