However if the user record is not found or the user already has vip_until >= CURRENT_TIMESTAMP (i.e. the user has already purchased "vip status") I would like to cancel the INSERT.
You can "join" two DDL commands by using a Common Table Expression (CTE) (i.e., WITH / SELECT). You would need to make it so the UPDATE happens first and if there are no results the INSERT simply becomes a no-op.
and the following works (if I change the function return type to VOID):
CREATE OR REPLACE FUNCTION words_buy_vip(
in_sid text,
in_social integer,
in_tid text,
in_item text,
in_price float,
in_ip inet)
RETURNS void AS
$func$
WITH cte AS (
UPDATE words_users u
SET vip_until = CURRENT_TIMESTAMP + interval '1 year'
FROM words_social s
WHERE s.sid = in_sid
AND s.social = in_social
AND u.uid = s.uid
AND (u.vip_until IS NULL OR u.vip_until < CURRENT_TIMESTAMP)
RETURNING
u.uid AS uid,
in_sid AS sid,
in_social AS social,
in_tid AS tid,
in_price AS price,
in_ip AS ip
)
INSERT INTO words_payments (
sid,
social,
tid,
paid,
price,
ip
) SELECT
sid,
social,
tid,
CURRENT_TIMESTAMP,
price,
ip
FROM cte
-- RETURNING uid;
$func$ LANGUAGE sql;
But I wonder how to return the uid in the above statement?
