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我有一个使用JomSocial的Joomla网站。我有一个.NET网络应用程序，我正在努力，最终将取代Joomla，因为我更喜欢.NET over PHP。现在我有.NET用户正在使用的移动网站。LINQ性能问题
LINQ to Entity使开发非常迅速，但我现在正在尝试解决性能问题。相互发送消息是＃1活动，迄今为止发送了超过40k条消息。这也是我遇到性能问题的地方。以下是JomSocial用于存储消息的两个表格。下面是我正在使用的当前LINQ代码，它返回我想要的结果，仅需两秒即可完成。
我认为通过列名你可能会弄清楚数据是什么样子，但如果没有，我可以创建一些，然后在这里发布一些，因为我必须用尽一点点。我应该提到的是，我正在使用带有.NET 3.5和MySQL w/MySQL .NET Connector的实体框架。
表：
delimiter $$
CREATE TABLE `jos_community_msg` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`from` int(10) unsigned NOT NULL,
`parent` int(10) unsigned NOT NULL,
`deleted` tinyint(3) unsigned DEFAULT '0',
`from_name` varchar(45) NOT NULL,
`posted_on` datetime DEFAULT NULL,
`subject` tinytext NOT NULL,
`body` text NOT NULL,
PRIMARY KEY (`id`),
KEY `parent` (`parent`),
KEY `deleted` (`deleted`),
KEY `from` (`from`)
) ENGINE=MyISAM AUTO_INCREMENT=340 DEFAULT CHARSET=utf8$$
delimiter $$
CREATE TABLE `jos_community_msg_recepient` (
`msg_id` int(10) unsigned NOT NULL,
`msg_parent` int(10) unsigned NOT NULL DEFAULT '0',
`msg_from` int(10) unsigned NOT NULL,
`to` int(10) unsigned NOT NULL,
`bcc` tinyint(3) unsigned DEFAULT '0',
`is_read` tinyint(3) unsigned DEFAULT '0',
`deleted` tinyint(3) unsigned DEFAULT '0',
UNIQUE KEY `un` (`msg_id`,`to`),
KEY `msg_id` (`msg_id`),
KEY `to` (`to`),
KEY `idx_isread_to_deleted` (`is_read`,`to`,`deleted`),
KEY `from` (`msg_from`),
KEY `parent` (`msg_parent`),
KEY `deleted` (`deleted`),
KEY `to_deleted` (`deleted`,`to`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8$$
LINQ：
var messages = (
from b in context.jos_community_msg
join i in (
from i in context.jos_community_msg_recepient
join a in context.jos_community_msg on i.msg_id equals a.id
where i.to == userId && && a.deleted == 0
group a by a.parent into g
select g.Max(p => p.id)) on b.id equals i
join a in context.jos_community_msg_recepient on i equals a.msg_id
orderby b.id descending
select new MessageHeaderItem()
{
IsDeleted = false,
IsRead = (a.is_read.Value == 0) ? false : true,
MessageId = b.parent,
Sent = b.posted_on.Value,
Subject = b.subject,
UserId = a.msg_from
});
total = messages.Count();
return messages.Skip(start).Take(max).ToList();
我已经尝试了一堆的变化，但没有任何已经快成功了。使用子选择对性能不利，但我不知道如何从该表中获取消息链中的最后一条消息。
更新： 这里是正在生成的SQL：
SELECT
`Limit1`.`C1`,
`Limit1`.`C2`,
`Limit1`.`C3`,
`Limit1`.`parent`,
`Limit1`.`posted_on`,
`Limit1`.`subject`,
`Limit1`.`msg_from`,
`Limit1`.`C4`,
`Limit1`.`C5`,
`Limit1`.`C6`
FROM (SELECT
`Extent1`.`id`,
`Extent1`.`parent`,
`Extent1`.`posted_on`,
`Extent1`.`subject`,
`Extent6`.`msg_from`,
1 AS `C1`,
cast(0 as decimal(0,0)) AS `C2`,
CASE WHEN (0 = (`Extent6`.`is_read`)) THEN (cast(0 as decimal(0,0))) ELSE (cast(1 as decimal(0,0))) END AS `C3`,
'Test' AS `C4`,
'' AS `C5`,
'' AS `C6`
FROM `jos_community_msg` AS `Extent1` INNER JOIN (SELECT
(SELECT
Max(`Extent5`.`id`) AS `A1`
FROM (SELECT
`jos_community_msg_recepient`.`bcc`,
`jos_community_msg_recepient`.`deleted`,
`jos_community_msg_recepient`.`is_read`,
`jos_community_msg_recepient`.`msg_from`,
`jos_community_msg_recepient`.`msg_id`,
`jos_community_msg_recepient`.`msg_parent`,
`jos_community_msg_recepient`.`to`
FROM `jos_community_msg_recepient` AS `jos_community_msg_recepient`) AS `Extent4` INNER JOIN `jos_community_msg` AS `Extent5` ON (`Extent4`.`msg_id` = `Extent5`.`id`) OR ((`Extent4`.`msg_id` IS NULL) AND (`Extent5`.`id` IS NULL))
WHERE ((`Extent4`.`to` = 62) AND (0 = (`Extent5`.`deleted`))) AND ((`Extent5`.`parent` = `Project2`.`parent`) OR ((`Extent5`.`parent` IS NULL) AND (`Project2`.`parent` IS NULL)))) AS `C1`
FROM (SELECT
62 AS `p__linq__5`,
`Distinct1`.`parent`
FROM (SELECT DISTINCT
`Extent3`.`parent`
FROM (SELECT
`jos_community_msg_recepient`.`bcc`,
`jos_community_msg_recepient`.`deleted`,
`jos_community_msg_recepient`.`is_read`,
`jos_community_msg_recepient`.`msg_from`,
`jos_community_msg_recepient`.`msg_id`,
`jos_community_msg_recepient`.`msg_parent`,
`jos_community_msg_recepient`.`to`
FROM `jos_community_msg_recepient` AS `jos_community_msg_recepient`) AS `Extent2` INNER JOIN `jos_community_msg` AS `Extent3` ON (`Extent2`.`msg_id` = `Extent3`.`id`) OR ((`Extent2`.`msg_id` IS NULL) AND (`Extent3`.`id` IS NULL))
WHERE (`Extent2`.`to` = 62) AND (0 = (`Extent3`.`deleted`))) AS `Distinct1`) AS `Project2`) AS `Project3` ON (`Extent1`.`id` = `Project3`.`C1`) OR ((`Extent1`.`id` IS NULL) AND (`Project3`.`C1` IS NULL)) INNER JOIN (SELECT
`jos_community_msg_recepient`.`bcc`,
`jos_community_msg_recepient`.`deleted`,
`jos_community_msg_recepient`.`is_read`,
`jos_community_msg_recepient`.`msg_from`,
`jos_community_msg_recepient`.`msg_id`,
`jos_community_msg_recepient`.`msg_parent`,
`jos_community_msg_recepient`.`to`
FROM `jos_community_msg_recepient` AS `jos_community_msg_recepient`) AS `Extent6` ON (`Project3`.`C1` = `Extent6`.`msg_id`) OR ((`Project3`.`C1` IS NULL) AND (`Extent6`.`msg_id` IS NULL))
ORDER BY
`id` DESC LIMIT 0,16) AS `Limit1`;
下面是从MySQL的解释：
1 PRIMARY <derived2> ALL 16
2 DERIVED <derived3> ALL 55 Using temporary; Using filesort
2 DERIVED Extent1 eq_ref PRIMARY PRIMARY 4 Project3.C1 1 Using where
2 DERIVED <derived9> ALL 333 Using where; Using join buffer
9 DERIVED jos_community_msg_recepient ALL 333
3 DERIVED <derived6> ALL 55
6 DERIVED <derived7> ALL 55
7 DERIVED <derived8> ALL 333 Using where; Using temporary
7 DERIVED Extent3 eq_ref PRIMARY,deleted PRIMARY 4 Extent2.msg_id 1 Using where; Distinct
8 DERIVED jos_community_msg_recepient ALL 333
4 DEPENDENT SUBQUERY Extent5 ref PRIMARY,parent,deleted parent 4 Project2.parent 2 Using where
4 DEPENDENT SUBQUERY <derived5> ALL 333 Using where; Using join buffer
5 DERIVED jos_community_msg_recepient ALL 333
这实际上是与MySQL。我将使用慢查询日志中的计数部分更新我的帖子。也许我需要在LINQ中改变一些东西。 – GregInWI2 2010-09-20 16:25:09
对不起。虽然您当然不能使用Microsoft工具，但我的建议仍然存在。找出执行确切的查询并查看问题出在哪里。你将不得不分析这个。也有用于MySql的工具。 – Steven 2010-09-20 16:31:33
对，我明白这一点。这些信息现在可以在这里找到。我很想知道我可以在LINQ中更改哪些内容，以便生成更好的查询。如果什么都不能改变，那么我想我必须使用动态SQL或过程。 – GregInWI2 2010-09-20 16:39:37