Tom Lane wrote:
>
> The Hermit Hacker <scrappy@hub.org> writes:
> > MySQL: 0.498u 0.150s 0:02.50 25.6% 10+1652k 0+0io 0pf+0w
> > PgSQL: 0.494u 0.061s 0:19.78 2.7% 10+1532k 0+0io 0pf+0w
> > From the 'time' numbers, MySQL is running ~17sec faster, but uses up 23%
> > more CPU to do this...so where is our slowdown?
>
> It's gotta be going into I/O, obviously. (I hate profilers that can't
> count disk accesses...) My guess is that the index scans are losing
> because they wind up touching too many disk pages. You show
>
On that particular machine that can be verified easily, I hope.
(there seems to be enough RAM). You can simply issue 10 to 100 such
queries in a row. Hopefully after the first query all needed info
will be in a disk cache, so the rest queries will not draw info from
disk. That will be a clean experiment.
--
Leon.
-------
He knows he'll never have to answer for any of his theories actually
being put to test. If they were, they would be contaminated by reality.