Re: So, is COUNT(*) fast now?

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

> I had wondered whether it'd be worth optimizing that along the
> lines of slot_getallattrs(). But most indexes probably have only
> one column, or anyway not enough to make for a useful savings.

>From a heavily-used production database:

cir=> select indnatts, count(*) from pg_index group by indnatts
order by indnatts;
indnatts | count
----------+-------
1 | 200
2 | 684
3 | 155
4 | 76
5 | 43
6 | 13
7 | 2
9 | 1
(8 rows)

This includes system table and TOAST table indexes (which seem to
have two columns). There are over 400 user tables, each of which
has a primary key, so most primary keys in our database are more
than one column.

-Kevin