Re: Decrease in performance with 7.3/optimizing a query

On Sun, 22 Dec 2002 21:31:30 -0500
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Don't suppose you have the query plan that was used in 7.2?

First, a correction: the previous version of Postgres was 7.1.2 - I apologize
for transposing the minor version digits.

Unfortunately, that previous version no longer runs due to incompatibilities
with upgraded libraries - however, I can look into rebuilding it if you think
that's a worthwhile avenue to pursue.

> Are you sure 7.3 is configured the same as 7.2?

Comparing the current and previous conf files, the only changes to default I
had made were to sort_mem and shared_buffers (to 8192 and 256 respectively). I
tried increasing the sort_mem (to 65536, higher values made no additional
difference) and was able to shave off about 7-8 seconds. It makes me wonder how
it would've affected the query under 7.1.2.

> sort_mem and locale setting in particular. You could be losing just on
> the extra sort time needed for a non-C-locale sort.

I don't see any setting described in postgresql.conf and playing around with
LANG in the environment didn't make any difference. Is there somewhere in
particular that I should be looking to set this? It sounds intriguing with
regards to my problem.

Thanks,
Harry