Search Postgresql Archives

Re: PostgreSQL Gotchas

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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

---------------------------(end of broadcast)---------------------------
TIP 6: explain analyze is your friend

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux