hash aggregation
От | Korisk |
---|---|
Тема | hash aggregation |
Дата | |
Msg-id | 118871349885342@web16f.yandex.ru обсуждение исходный текст |
Ответы |
Re: hash aggregation
|
Список | pgsql-performance |
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=25259817loops=1) Output: id, name, value Total runtime: 10351.989 ms (9 rows) hashes=# Thank you.
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