| From: | Christopher Kings-Lynne <chris(dot)kings-lynne(at)calorieking(dot)com> |
|---|---|
| To: | PFC <lists(at)peufeu(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, mario(dot)splivalo(at)mobart(dot)hr, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: SELECT FOR UPDATE performance is bad |
| Date: | 2006-04-19 02:21:35 |
| Message-ID: | 44459EAF.2030601@calorieking.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
> Suppose you have a table codes :
> (
> game_id INT,
> code TEXT,
> used BOOL NOT NULL DEFAULT 'f',
> prize ...
> ...
> PRIMARY KEY (game_id, code)
> )
>
> Just UPDATE codes SET used='t' WHERE used='f' AND game_id=... AND
> code=...
>
> Then check the rowcount : if one row was updated, the code was not
> used yet. If no row was updated, the code either did not exist, or was
> already used.
You can use a stored procedure with exceptions no?
Try this:
Chris
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