| From: | Michael Fuhr <mike(at)fuhr(dot)org> |
|---|---|
| To: | Jeffrey Melloy <jmelloy(at)visualdistortion(dot)org> |
| Cc: | Neil Conway <neilc(at)samurai(dot)com>, "Aly S(dot)P Dharshi" <aly(dot)dharshi(at)telus(dot)net>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: PostgreSQL Gotchas |
| Date: | 2005-10-06 23:42:05 |
| Message-ID: | 20051006234205.GA73899@winnie.fuhr.org |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
On Thu, Oct 06, 2005 at 05:47:36PM -0500, Jeffrey Melloy wrote:
> The only thing I could see actually being an issue is the random() one
> and add missing from. The rest are trivial. The random() thing is
> interesting, esoteric, and probably has never been a problem in a real
> situation. (Or has exactly once, when he wrote that gotcha)
The random() issue has a workaround that the gotchas page doesn't
mention:
SELECT id, is_true
FROM (SELECT id, RANDOM() < 0.5 AS is_true FROM some_table OFFSET 0) AS t_tmp
WHERE is_true;
Tom Lane brought up the OFFSET 0 trick a couple of days ago in the
"Avoiding evaluating functions twice" thread:
http://archives.postgresql.org/pgsql-general/2005-10/msg00107.php
--
Michael Fuhr
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