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我有一个select语句,使一个非常简单的查询从一个更复杂的看法:索引与Postgresql连接的视图?
我有一个相当直接的select语句....
SELECT
uid
FROM userpermissions
WHERE
uid = :whoami
AND
application = :application
AND
subsystem = :subsystem
;
而我的观点是唯一的整数和varchars,但加入了四张表(可能是真正的问题)。
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;
我不确定如何有效地更新视图,使我的查询是更有效,因为他们需要大约1-4秒,现在,在某些情况下,高达8
我的另一个想法是使用memcache,但这对于低效率的问题就像是一个创可贴的解决方案。
这里的选择的一个配置文件:
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)
这完全令我感到困惑,因为我把它改成PDO与PHP查询此刻只需几秒钟,一秒钟的不是分数。
使用pg_query需要多长时间?而且,你的数据库服务器有多远? – doctore 2012-01-16 16:16:26
DB和Web是同一台机器。上面的命令行psql指示0.192ms,当从PHP调用时指示3.6 *秒*。 – Incognito 2012-01-16 16:18:32
0.192 ms这是数据库服务器中的时间,但是如果使用PDO函数的PHP实例的函数pg_query,需要多长时间? – doctore 2012-01-16 16:30:57