Re: ORDER BY random() LIMIT 1 slowness

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> "Gavin M. Roy" <gmr(at)justsportsusa(dot)com> writes:
> > SELECT * FROM poetry ORDER BY random() LIMIT 1;
> > [ is slow for 35000 rows ]
>
> Yeah. Basically this query is implemented as
> (a) select all 35000 rows of "poetry";
> (b) compute a random() value for each row;
> (c) sort by the random() values;
> (d) take the first row, discard the rest.

If you can generate a random value from your application layer you could do

select * from poetry LIMIT 1 OFFSET <random value>

Can offset values be placeholders in prepared queries? If not then this has
that disadvantage.

--
greg