Re: Selecting random rows efficiently
От
Jeff
Тема
Re: Selecting random rows efficiently
Дата
Msg-id
Pine.BSF.4.44.0308300905390.829-100000@torgo.978.org
Ответ на
Selecting random rows efficiently (Richard Jones)
Список
Дерево обсуждения
Re: Hardware recommendations to scale to silly load Vivek Khera <khera@kcilink.com>
Re: Hardware recommendations to scale to silly load "Matt Clark" <matt@ymogen.net>
On Sat, 30 Aug 2003, Richard Jones wrote:
> Hi,
> i have a table of around 3 million rows from which i regularly (twice a second
> at the moment) need to select a random row from
>
> currently i'm doing "order by rand() limit 1" - but i suspect this is
> responsible for the large load on my db server - i guess that PG is doing far
> too much work just to pick one row.
>
If you have an int id (aka serial) column then it is simple - just pick a
random number between 1 and currval('id_seq')...
or offset rand() limit 1 perhaps?
since you want random ther eis no need to bother with an order and that'll
save a sort.
--
Jeff Trout
http://www.jefftrout.com/
http://www.stuarthamm.net/
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