Re: Re: Mapping output from a SEQUENCE into something non-repeating/colliding but random-looking?

Jasen Betts wrote:

> That means storing a long list of numbers and doing queries similar to
> the following to get ne next value for the sequence.
>
> select id from idtable
> order by id
> limit 1
> offset random(0, (select count (*) from idtable)
>
> a ramdom-looking 1:1 mapping is potentially much more efficient.

You'd probably be better off generating it with something like:

CREATE TABLE shuffled AS (n integer, s integer)
AS SELECT n, NULL FROM generate_series(0, max_value) AS n;

SELECT shuffle(); -- sets `s' for each `n'

... then querying it with:

SELECT s FROM shuffled WHERE n = <value-wanted>;

... but you still have to generate, shuffle, and store a huge collection
of values.

--
Craig Ringer