From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Speeding up aggregates |
Date: | 2002-12-07 01:54:43 |
Message-ID: | 200212061754.43566.josh@agliodbs.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
Tom,
We have a winner on simple aggregates:
Version 7.2.3:
explain analyze select client_id, count(*) from case_clients group by
client_id;
NOTICE: QUERY PLAN:
Aggregate (cost=11892.51..12435.75 rows=10865 width=4) (actual
time=1162.27..1569.40 rows=436 loops=1)
-> Group (cost=11892.51..12164.13 rows=108648 width=4) (actual
time=1162.24..1477.70 rows=108648 loops=1)
-> Sort (cost=11892.51..11892.51 rows=108648 width=4) (actual
time=1162.22..1280.64 rows=108648 loops=1)
-> Seq Scan on case_clients (cost=0.00..2804.48 rows=108648
width=4) (actual time=0.07..283.14 rows=108648 loops=1)
Total runtime: 2387.87 msec
Versus Version 7.4devel:
explain analyze select client_id, count(*) from case_clients group by
client_id;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------
HashAggregate (cost=3289.72..3289.84 rows=46 width=4) (actual
time=447.80..448.71 rows=436 loops=1)
-> Seq Scan on case_clients (cost=0.00..2746.48 rows=108648 width=4)
(actual time=0.08..267.45 rows=108648 loops=1)
Total runtime: 473.77 msec
(3 rows)
However, more complex queries involving aggregates seem to be unable to make
use of the hashaggregate. I'll get back to you when I know what the
breakpoint is.
--
-Josh Berkus
______AGLIO DATABASE SOLUTIONS___________________________
Josh Berkus
Complete information technology josh(at)agliodbs(dot)com
and data management solutions (415) 565-7293
for law firms, small businesses fax 621-2533
and non-profit organizations. San Francisco
From | Date | Subject | |
---|---|---|---|
Next Message | Fred Moyer | 2002-12-07 02:16:43 | Query optimization |
Previous Message | Josh Berkus | 2002-12-07 00:38:18 | Re: query question |