Re: conditional rule not applied

On Wed, 30 Dec 2009 19:39:15 -0600,
Seb <spluque(at)gmail(dot)com> wrote:

> CREATE RULE footwear_nothing_upd AS
> ON UPDATE TO footwear DO INSTEAD NOTHING;
> CREATE RULE footwear_newshoelaces_upd AS
> ON UPDATE TO footwear
> WHERE NEW.sl_name <> OLD.sl_name AND OLD.sl_name IS NULL
> DO
> INSERT INTO shoelaces (sh_id, sl_name)
> VALUES(NEW.sh_id, NEW.sl_name);

I think my error is in the test expression, which doesn't deal properly
with the null value, so correcting:

CREATE RULE footwear_nothing_upd AS
ON UPDATE TO footwear DO INSTEAD NOTHING;
CREATE RULE footwear_newshoelaces_upd AS
ON UPDATE TO footwear
WHERE NEW.sl_name IS DISTINCT FROM OLD.sl_name AND OLD.sl_name IS NULL
DO
INSERT INTO shoelaces (sh_id, sl_name)
VALUES(NEW.sh_id, NEW.sl_name);

However, could a more direct and robust test for an inexistent record in
'shoelaces' be made?

--
Seb