Performance testing of COPY (SELECT) TO

Hi,

we have a large export here, I made an in-house benchmark
between Informix, plain PostgreSQL-8.1.4 and
8.2devel+COPY(SELECT) using the same data and query.
Find the results below for the two PostgreSQL versions.
With PostgreSQL 8.1.4, I used this:

begin;
select ... into temp myquery1;
copy myquery1 to stdout csv delimiter '|';
rollback;

With 8.2devel, I simple used
copy (select ...) to stdout csv delimiter '|';

# of clients:            1*        3**        10**
PostgreSQL        1:33        10:58        55:46
PostgreSQL 8.2        1:19        4:55        18:28

*  - average of 4 runs, the first was with cold caches after reboot
** - 1 run, average of cliens' runtimes

Performance between 8.1.4 and 8.2devel is interesting:
1 client: 15%
3 clients: 55.2%
10 clients: 66.9%

The same machine was used for testing.

Best regards,
Zoltán Böszörményi