Re: New version of money type

On Fri, 15 Sep 2006 16:15:04 -0000
Andrew - Supernews <andrew+nonews@supernews.com> wrote:
> On 2006-09-15, "D'Arcy J.M. Cain" <darcy@druid.net> wrote:
> >> Seems? Have you benchmarked it?
> >
> > Not rigourously but a few "ANALYZE EXPLAIN" statements bear out this
> > observation.
> 
> The overhead of EXPLAIN ANALYZE is so large that it completely swamps any
> real difference.

Hence my "not rigourously" comment.

> First measure the benchmark overhead:
> 
> select null::integer from generate_series(1,1000) s1,
>                           generate_series(1,1000) s2;

Time: 870.531 ms

> Since output functions are strict, this does not call int4out at all, so
> this measures the time taken to generate the million rows, output and discard
> them.
> 
> Then do the real tests:
> 
> select 0::integer from generate_series(1,1000) s1,
>                        generate_series(1,1000) s2;

Time: 1410.690 ms

> This calls int4out(0) a million times. (the input function is only called
> once since it is a constant, and therefore handled during planning)
> 
> select 0::numeric from generate_series(1,1000) s1,
>                        generate_series(1,1000) s2;

Time: 1256.539 ms

Selecting "'0'::money" gives:

Time: 1487.757 ms

Bigint gives:

Time: 1450.405 ms

The extra processing over int and bigint is probably due to locale
formatting.  That's partially why I was wondering if the basic type
should be doing that as opposed to doing it in app code.  Also, I
wonder if some of the techniques in numeric could be applied here.  I
haven't looked carefully at the numeric output code yet.

In any case, I/O speed is probably not that important with this type.
Internal calculations, in my experience, are much more critical.

-- 
D'Arcy J.M. Cain <darcy@druid.net>         |  Democracy is three wolves
http://www.druid.net/darcy/                |  and a sheep voting on
+1 416 425 1212     (DoD#0082)    (eNTP)   |  what's for dinner.