Thank you Brian and others, but -
On Fri, Sep 9, 2016 at 5:22 PM, Brian Dunavant <brian@xxxxxxxxxx> wrote:
I'm making the assumption that you only have one ip/user in words_users.
with lockrow as (
SELECT g.gid, u.ip
FROM words_games g join words_users u
ON (g.player1 = u.uid)
WHERE g.finished IS NULL
AND g.player1 <> in_uid
AND g.played1 IS NOT NULL
AND g.player2 IS NULL
LIMIT 1
FOR UPDATE SKIP LOCKED
), do_the_update as (
UPDATE words_games g1
SET player2 = in_uid
FROM lockrow g2
WHERE g1.gid = g2.gid
RETURNING g1.gid, g1.player2
)
select m.gid into out_gid, u.ip into out_uip
from do_the_update m
join lockrow u on (gid)
;
The general idea being lock the row in the first CTE, update it in the
second, returning your values, and then query against those in the
final select to get the ip. If it didn't update anything, you'll get
no results.
unfortunately, the above query does not seem to ensure, that players with same ip can not join the same game, which is actually my question...
But thanks for showing the CTE for UPDATE ... RETURNING - that is probably the way to go for me
Regards
Alex
