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我有一個select語句,使一個非常簡單的查詢從一個更復雜的看法:索引與Postgresql連接的視圖?
我有一個相當直接的select語句....
SELECT
uid
FROM userpermissions
WHERE
uid = :whoami
AND
application = :application
AND
subsystem = :subsystem
;
而我的觀點是唯一的整數和varchars,但加入了四張表(可能是真正的問題)。
View "public.userpermissions"
Column | Type | Modifiers | Storage | Description
-------------+------------------------+-----------+----------+-------------
uid | integer | | plain |
gid | integer | | plain |
sid | integer | | plain |
name | character varying(128) | | extended |
application | character varying(128) | | extended |
subsystem | character varying(128) | | extended |
View definition:
SELECT users.uid, groups.gid, groupaccess.sid, groups.name, subsystems.application, subsystems.subsystem
FROM users
JOIN groups ON groups.gid = users.gid
JOIN groupaccess ON groups.gid = groupaccess.gid
JOIN subsystems ON subsystems.sid = groupaccess.sid;
我不確定如何有效地更新視圖,使我的查詢是更有效,因爲他們需要大約1-4秒,現在,在某些情況下,高達8
我的另一個想法是使用memcache,但這對於低效率的問題就像是一個創可貼的解決方案。
這裏的選擇的一個配置文件:
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=1.18..4.54 rows=1 width=4) (actual time=0.043..0.043 rows=0 loops=1)
Join Filter: (groups.gid = users.gid)
-> Nested Loop (cost=1.18..3.34 rows=1 width=8) (actual time=0.040..0.040 rows=0 loops=1)
-> Hash Join (cost=1.18..2.78 rows=1 width=4) (actual time=0.039..0.039 rows=0 loops=1)
Hash Cond: (groupaccess.sid = subsystems.sid)
-> Seq Scan on groupaccess (cost=0.00..1.43 rows=43 width=8) (actual time=0.014..0.014 rows=1 loops=1)
-> Hash (cost=1.17..1.17 rows=1 width=4) (actual time=0.017..0.017 rows=0 loops=1)
Buckets: 1024 Batches: 1 Memory Usage: 0kB
-> Seq Scan on subsystems (cost=0.00..1.17 rows=1 width=4) (actual time=0.015..0.015 rows=0 loops=1)
Filter: (((application)::text = 'LoginLink'::text) AND ((subsystem)::text = '1'::text))
-> Index Scan using groups_pkey on groups (cost=0.00..0.55 rows=1 width=4) (never executed)
Index Cond: (gid = groupaccess.gid)
-> Seq Scan on users (cost=0.00..1.19 rows=1 width=8) (never executed)
Filter: (uid = 2)
Total runtime: 0.192 ms
(15 rows)
這完全令我感到困惑,因爲我把它改成PDO與PHP查詢此刻只需幾秒鐘,一秒鐘的不是分數。
使用pg_query需要多長時間?而且,你的數據庫服務器有多遠? – doctore 2012-01-16 16:16:26
DB和Web是同一臺機器。上面的命令行psql指示0.192ms,當從PHP調用時指示3.6 *秒*。 – Incognito 2012-01-16 16:18:32
0.192 ms這是數據庫服務器中的時間,但是如果使用PDO函數的PHP實例的函數pg_query,需要多長時間? – doctore 2012-01-16 16:30:57