Re: Much Ado About COUNT(*)

On Wed, Jan 19, 2005 at 14:59:17 -0000,
Mark Cave-Ayland <m(dot)cave-ayland(at)webbased(dot)co(dot)uk> wrote:
> BEGIN;
> INSERT INTO person (first_name, .... Tel) VALUES ('Fred', ....
> '12345');
> INSERT INTO person_count(id) VALUES (currval('id_seq'));
> COMMIT;
>
>
> So then I would use SELECT COUNT(*) FROM person_count whenever I wanted to
> know the current number of person records. How much quicker would a COUNT(*)
> be if visibility were included in the indices as opposed to a "hacked"
> approach like this?

You are only going to get a constant factor speed up unless the space savings
allows much better use of cache. You probably want to look at using
triggers to maintain counts in another table.