From: | Ron Johnson <ron(dot)l(dot)johnson(at)cox(dot)net> |
---|---|
To: | PgSQL Performance ML <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Selecting random rows efficiently |
Date: | 2003-08-30 14:04:01 |
Message-ID: | 1062252240.667.453.camel@haggis |
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Lists: | pgsql-hackers pgsql-performance |
On Sat, 2003-08-30 at 08:09, 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.
What datatype is the selected by key?
Also, where is rand() defined? Is that a UDF?
Could it be that there is a type mismatch?
> one way i can think of is to read in all the primary keys from my table, and
> select one of the keys at random then directly fetch that row.
>
> are there any other ways to do this? i need to keep the load down :)
>
> Thanks,
> Richard
Are you really in Micronesia?
--
-----------------------------------------------------------------
Ron Johnson, Jr. ron(dot)l(dot)johnson(at)cox(dot)net
Jefferson, LA USA
"The greatest dangers to liberty lurk in insidious encroachment
by men of zeal, well-meaning, but without understanding."
Justice Louis Brandeis, dissenting, Olmstead v US (1928)
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