From: Korisk <Korisk@yandex.ru>
To: pgsql-performance@postgresql.org
Subject: hash aggregation
Date: Wed, 10 Oct 2012 20:09:02 +0400
Message-ID: <118871349885342@web16f.yandex.ru> (raw)
Hello! Is it possible to speed up the plan?
hashes=# \d hashcheck
Table "public.hashcheck"
Column | Type | Modifiers
--------+-------------------+--------------------------------------------------------
id | integer | not null default nextval('hashcheck_id_seq'::regclass)
name | character varying |
value | character varying |
Indexes:
"btr" btree (name)
hashes=# select version();
version
--------------------------------------------------------------------------------------------------------------
PostgreSQL 9.2.1 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.7.2 20120921 (Red Hat 4.7.2-2), 64-bit
(1 row)
hashes=# explain analyse verbose select name, count(name) as cnt from hashcheck group by name order by name desc;
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------
Sort (cost=573977.88..573978.38 rows=200 width=32) (actual time=10351.280..10351.551 rows=4000 loops=1)
Output: name, (count(name))
Sort Key: hashcheck.name
Sort Method: quicksort Memory: 315kB
-> HashAggregate (cost=573968.24..573970.24 rows=200 width=32) (actual time=10340.507..10341.288 rows=4000 loops=1)
Output: name, count(name)
-> Seq Scan on public.hashcheck (cost=0.00..447669.16 rows=25259816 width=32) (actual time=0.019..2798.058 rows=25259817 loops=1)
Output: id, name, value
Total runtime: 10351.989 ms
(9 rows)
hashes=#
Thank you.
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To: pgsql-performance@postgresql.org
Cc: Korisk@yandex.ru
Subject: Re: hash aggregation
In-Reply-To: <118871349885342@web16f.yandex.ru>
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