最近我有这个question,一切正常,直到我把它发送到我的服务器在DreamHost。如何提高此查询的性能?
下面的查询似乎需要太长的时间来执行,我不知道为什么这么多行一次处理。在我的本地服务器中,相同的查询在0.3秒内执行完毕。
SELECT feed_entries . *
FROM feed_entries
WHERE
id
IN (
SELECT e.id
FROM feed_entries AS e
INNER JOIN feeds AS f ON e.feed_id = f.id
INNER JOIN entries_categorias AS ec ON ec.entry_id = e.id
INNER JOIN categorias AS c ON ec.categoria_id = c.id
WHERE
e.deleted =0
AND
c.slug
IN ('entenda', 'google')
GROUP BY e.id
HAVING COUNT(DISTINCT ec.id) =2
)
ORDER BY date DESC
LIMIT 1
这是我从支持团队收到的消息:
嗯,它看起来像该查询 锁定由于这些其他查询 像这样的加工6.5百万 记录,持续11秒。
# Query_time: 11.639269 Lock_time: 0.000192 Rows_sent: 2 Rows_examined:
6509098
use desenvolvimentistas;
SET timestamp=1280325753;
SELECT `e`.*, `f`.`titulo` AS `feedTitulo`, `f`.`url` AS `feedUrl` FROM
`feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id WHERE (e.id IN (SELECT
`e`.`id` FROM `feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id =e.id
INNER JOIN `categorias` AS `c` ON ec.categoria_id =c.id WHERE (e.deleted
=0) AND (e.id NOT IN ('', '', '842', '853', '774', '878')) AND
(e.imagem145x145 =1) AND (c.slug IN('destaque-2')) GROUP BY `e`.`id`
HAVING (COUNT(DISTINCT ec.id) =1))) ORDER BY `e`.`date` DESC LIMIT 4;
有可能的查询需要在本地计算机是 空闲的0.3秒到 运行,但因为它是在 一次运行查询150这是在我们的服务器上 缓慢,并且每一个正在处理 1530万条记录。
我有我们的MySQL管理员看了看 它,他说,这是相当低效 和感到惊讶的是 数据库甚至访问,因为 查询没有这么锁定。他说 表示数据库将被禁用,如果 它继续这种方式并导致 服务器问题。他说你应该修复所检查的行或者获得一个MySQL PS,尽管mysql ps不会修复 它,而是只会阻止 数据库被禁用。
下面是该查询:
# Query_time: 25.944779 Lock_time: 0.000176 Rows_sent: 0 Rows_examined:
15378209
use desenvolvimentistas;
SELECT `feed_entries`.* FROM `feed_entries` WHERE (id IN (SELECT `e`.`id`
FROM `feed_entries` AS `e` INNER JOIN `feeds` AS `f` ON e.feed_id =f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id =e.id INNER JOIN
`categorias` AS `c` ON ec.categoria_id =c.id WHERE (e.deleted =0) AND
(c.slug IN('entenda','google')) GROUP BY `e`.`id` HAVING (COUNT(DISTINCT
ec.id) =2))) ORDER BY `date` DESC LIMIT 1;
这里是另一个需要被固定:
# Query_time: 27.010857 Lock_time: 0.000165 Rows_sent: 0 Rows_examined:
15382750
use desenvolvimentistas;
SET timestamp=1280325706;
SELECT `e`.*, `f`.`titulo` AS `feedTitulo`, `f`.`url` AS `feedUrl` FROM
`feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id WHERE (e.id IN (SELECT
`e`.`id` FROM `feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id =e.id
INNER JOIN `categorias` AS `c` ON ec.categoria_id =c.id WHERE (e.deleted
=0) AND (c.slug IN('manchete', 'google')) GROUP BY `e`.`id` HAVING
(COUNT(DISTINCT ec.id) =2))) ORDER BY `e`.`date` DESC LIMIT 4;7:18
因为他命令它,但只取得最好的结果,是否有一个好的建议可以有'日期'的索引? – 2010-07-28 15:44:54
@Neil Trodden:是的,但是[MySQL对分配索引的空间有限制(MyISAM为1,000,InnoDB为767)](http://dev.mysql.com/doc/refman/5.0/en/create-index .html)所以JOIN标准是我的首要任务,然后看看我能做些什么来覆盖索引。 – 2010-07-28 15:59:19
谢谢,我减少了150个查询的数量并定义了索引。也发现了其他的错误。现在可以了。 – 2010-08-03 16:12:23