Mysql 什么是适当的作用域/索引，有助于通过rails使作用域查找更高效？
我有一个相对较大的4层关系数据设置，如下所示：Mysql 什么是适当的作用域/索引，有助于通过rails使作用域查找更高效？,mysql,ruby-on-rails,database,optimization,scope,Mysql,Ruby On Rails,Database,Optimization,Scope,我有一个相对较大的4层关系数据设置，如下所示： ClientApplication has_many => ClientApplicationVersions ClientApplicationVersions has_many => CloudLogs CloudLogs has_many => Logs ClientApplication.find_all_by_account_id(1).where(public_key:
ClientApplication has_many => ClientApplicationVersions
ClientApplicationVersions has_many => CloudLogs
CloudLogs has_many => Logs
ClientApplication.find_all_by_account_id(1).where(public_key: 'p0kZudG0').joins(:client_application_version).where("client_application_versions.public_key=?",'0HgoJRyE').logs.page(1)
YourObject.joins(:client_application).
where(ClientApplication.arel_table[:public_key].eq(client_application_key))
客户端应用程序-
…-
account\u id-
公钥-
deleted\u在客户端应用程序版本-
…-
client\u application\u id-
公钥-
deleted\u在cloud\u日志-…
-
client\u application\u version\u id-
公钥-
deleted\u在日志-
…-
cloud\u log\u id-
公钥-
时间戳-
deleted\u在我仍在发展中，所以结构和设置不是一成不变的，但我希望它是设置好。使用Rails 3.2.11和InnoDB MySQL。数据库当前填充了一小部分数据（与最终的数据库大小相比）（
logs帐户id客户端应用程序限制。公钥客户端应用程序版本。公钥帐户id客户端应用程序。公钥帐户id我正在使用rails作用域来帮助进行以下调用：
scope :account_id, proc {|account_id| joins(:client_application).where("client_applications.account_id = ?", account_id) }
scope :client_application_key, proc {|client_application_key| joins(:client_application).where("client_applications.public_key = ?", client_application_key) }
scope :client_application_version_key, proc {|client_application_version_key| joins(:client_application_version).where("client_application_versions.public_key = ?", client_application_version_key) }
default_scope order('logs.timestamp DESC')
公钥上的每个表上都有索引。我在logs
表上有几个索引，包括优化器更喜欢使用的索引（index\u logs\u on\u cloud\u log\u id
），但查询仍需要花费数代时间才能运行
下面是我如何在rails控制台中调用该方法的：
Log.account_id(1).client_application_key('p0kZudG0').client_application_version_key('0HgoJRyE').page(1)
。。。以下是rails将其转化为的内容：
SELECT `logs`.* FROM `logs` INNER JOIN `cloud_logs` ON `cloud_logs`.`id` = `logs`.`cloud_log_id` INNER JOIN `client_application_versions` ON `client_application_versions`.`id` = `cloud_logs`.`client_application_version_id` INNER JOIN `client_applications` ON `client_applications`.`id` = `client_application_versions`.`client_application_id` INNER JOIN `cloud_logs` `cloud_logs_logs_join` ON `cloud_logs_logs_join`.`id` = `logs`.`cloud_log_id` INNER JOIN `client_application_versions` `client_application_versions_logs` ON `client_application_versions_logs`.`id` = `cloud_logs_logs_join`.`client_application_version_id` WHERE (logs.deleted_at IS NULL) AND (client_applications.account_id = 1) AND (client_applications.public_key = 'p0kZudG0') AND (client_application_versions.public_key = '0HgoJRyE') ORDER BY logs.timestamp DESC LIMIT 100 OFFSET 0
。。。下面是该查询的解释语句
+----+-------------+----------------------------------+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------+---------+------------------------------------------------------------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------------------------+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------+---------+------------------------------------------------------------------------+------+----------------------------------------------+
| 1 | SIMPLE | client_application_versions | ref | PRIMARY,index_client_application_versions_on_client_application_id,index_client_application_versions_on_public_key | index_client_application_versions_on_public_key | 768 | const | 1 | Using where; Using temporary; Using filesort |
| 1 | SIMPLE | client_applications | eq_ref | PRIMARY,index_client_applications_on_account_id,index_client_applications_on_public_key | PRIMARY | 4 | cloudlog_production.client_application_versions.client_application_id | 1 | Using where |
| 1 | SIMPLE | cloud_logs | ref | PRIMARY,index_cloud_logs_on_client_application_version_id | index_cloud_logs_on_client_application_version_id | 5 | cloudlog_production.client_application_versions.id | 481 | Using where; Using index |
| 1 | SIMPLE | cloud_logs_logs_join | eq_ref | PRIMARY,index_cloud_logs_on_client_application_version_id | PRIMARY | 4 | cloudlog_production.cloud_logs.id | 1 | |
| 1 | SIMPLE | client_application_versions_logs | eq_ref | PRIMARY | PRIMARY | 4 | cloudlog_production.cloud_logs_logs_join.client_application_version_id | 1 | Using index |
| 1 | SIMPLE | logs | ref | index_logs_on_cloud_log_id_and_deleted_at_and_timestamp,index_logs_on_cloud_log_id_and_deleted_at,index_logs_on_cloud_log_id,index_logs_on_deleted_at | index_logs_on_cloud_log_id | 5 | cloudlog_production.cloud_logs.id | 4 | Using where |
+----+-------------+----------------------------------+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------+---------+------------------------------------------------------------------------+------+----------------------------------------------+
这个问题有三个部分：
我是否可以使用其他索引优化数据库，以帮助这些类型的连接相关排序查询变得更高效
我可以优化rails代码以帮助这类查找以更高效的方式运行吗
我是否只是在接近这个范围时为大型数据集找到了错误的方法
2012年1月24日更新
正如Geoff和J_MCCaffrey在回答中所建议的那样，我将查询分为3个不同的部分，以尝试隔离问题。正如所料，处理最大的表是一个问题。MYSQL优化器通过使用不同的索引以不同的方式处理此问题，但延迟仍然存在。下面是对这种方法的解释
ClientApplication.find_by_account_id_and_public_key(1, 'p0kZudG0').versions.select{|cav| cav.public_key = '0HgoJRyE'}.first.logs.page(2)
ClientApplication Load (165.9ms) SELECT `client_applications`.* FROM `client_applications` WHERE `client_applications`.`account_id` = 1 AND `client_applications`.`public_key` = 'p0kZudG0' AND (client_applications.deleted_at IS NULL) ORDER BY client_applications.id LIMIT 1
ClientApplicationVersion Load (105.1ms) SELECT `client_application_versions`.* FROM `client_application_versions` WHERE `client_application_versions`.`client_application_id` = 3 AND (client_application_versions.deleted_at IS NULL) ORDER BY client_application_versions.created_at DESC, client_application_versions.id DESC
Log Load (57295.0ms) SELECT `logs`.* FROM `logs` INNER JOIN `cloud_logs` ON `logs`.`cloud_log_id` = `cloud_logs`.`id` WHERE `cloud_logs`.`client_application_version_id` = 49 AND (logs.deleted_at IS NULL) AND (cloud_logs.deleted_at IS NULL) ORDER BY logs.timestamp DESC, cloud_logs.received_at DESC LIMIT 100 OFFSET 100
EXPLAIN (214.5ms) EXPLAIN SELECT `logs`.* FROM `logs` INNER JOIN `cloud_logs` ON `logs`.`cloud_log_id` = `cloud_logs`.`id` WHERE `cloud_logs`.`client_application_version_id` = 49 AND (logs.deleted_at IS NULL) AND (cloud_logs.deleted_at IS NULL) ORDER BY logs.timestamp DESC, cloud_logs.received_at DESC LIMIT 100 OFFSET 100
EXPLAIN for: SELECT `logs`.* FROM `logs` INNER JOIN `cloud_logs` ON `logs`.`cloud_log_id` = `cloud_logs`.`id` WHERE `cloud_logs`.`client_application_version_id` = 49 AND (logs.deleted_at IS NULL) AND (cloud_logs.deleted_at IS NULL) ORDER BY logs.timestamp DESC, cloud_logs.received_at DESC LIMIT 100 OFFSET 100
+----+-------------+------------+-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------+---------+-----------------------------------+------+-------------------------------------------------------------------------------------------------------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------+---------+-----------------------------------+------+-------------------------------------------------------------------------------------------------------------------------------------------------+
| 1 | SIMPLE | cloud_logs | index_merge | PRIMARY,index_cloud_logs_on_client_application_version_id,index_cloud_logs_on_deleted_at | index_cloud_logs_on_client_application_version_id,index_cloud_logs_on_deleted_at | 5,9 | NULL | 1874 | Using intersect(index_cloud_logs_on_client_application_version_id,index_cloud_logs_on_deleted_at); Using where; Using temporary; Using filesort |
| 1 | SIMPLE | logs | ref | index_logs_on_cloud_log_id_and_deleted_at_and_timestamp,index_logs_on_cloud_log_id_and_deleted_at,index_logs_on_cloud_log_id,index_logs_on_deleted_at | index_logs_on_cloud_log_id | 5 | cloudlog_production.cloud_logs.id | 4 | Using where |
+----+-------------+------------+-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------+---------+-----------------------------------+------+-------------------------------------------------------------------------------------------------------------------------------------------------+
2012年1月25日更新
以下是所有相关表格的索引：
CLIENT_APPLICATIONS:
PRIMARY KEY (`id`),
UNIQUE KEY `index_client_applications_on_key` (`key`),
KEY `index_client_applications_on_account_id` (`account_id`),
KEY `index_client_applications_on_deleted_at` (`deleted_at`),
KEY `index_client_applications_on_public_key` (`public_key`)
CLIENT_APPLICATION_VERSIONS:
PRIMARY KEY (`id`),
KEY `index_client_application_versions_on_client_application_id` (`client_application_id`),
KEY `index_client_application_versions_on_deleted_at` (`deleted_at`),
KEY `index_client_application_versions_on_public_key` (`public_key`)
CLOUD_LOGS:
PRIMARY KEY (`id`),
KEY `index_cloud_logs_on_api_client_version_id` (`api_client_version_id`),
KEY `index_cloud_logs_on_client_application_version_id` (`client_application_version_id`),
KEY `index_cloud_logs_on_deleted_at` (`deleted_at`),
KEY `index_cloud_logs_on_device_id` (`device_id`),
KEY `index_cloud_logs_on_public_key` (`public_key`),
KEY `index_cloud_logs_on_received_at` (`received_at`)
LOGS:
PRIMARY KEY (`id`),
KEY `index_logs_on_class_name` (`class_name`),
KEY `index_logs_on_cloud_log_id_and_deleted_at_and_timestamp` (`cloud_log_id`,`deleted_at`,`timestamp`),
KEY `index_logs_on_cloud_log_id_and_deleted_at` (`cloud_log_id`,`deleted_at`),
KEY `index_logs_on_cloud_log_id` (`cloud_log_id`),
KEY `index_logs_on_deleted_at` (`deleted_at`),
KEY `index_logs_on_file_name` (`file_name`),
KEY `index_logs_on_method_name` (`method_name`),
KEY `index_logs_on_public_key` (`public_key`),
KEY `index_logs_on_timestamp` USING BTREE (`timestamp`)
不幸的是，我的Rails优化经验都是使用PostgreSQL的，所以大部分可能都不适用。尽管如此，我还是有一些可能适用的建议：
尝试在您的作用域中使用连接
而不是包含
-包含
用于触发紧急加载-完全可能是您看到的一些减速是加载了不需要的模型。即使不是这样，使用连接
应该会生成一个更可读的查询-它的包含
将所有列别名为“t2_r8”，以此类推
此外，您还需要确保对任何可能被筛选的列进行索引-一般来说，以\u id
结尾的列可能会以这种方式被引用，并且可能应该被索引，以及在范围中专门筛选的任何列（如客户端应用程序版本\u密钥
）我写这篇文章是为了解决我自己的问题，希望能得到更好的答案。目前，数据库完全由关系型手册设置
ClientApplication has_many => ClientApplicationVersions
ClientApplicationVersions has_many => CloudLogs
CloudLogs has_many => Logs
这意味着，当我需要查找属于客户端应用程序的日志时，我必须进行3次额外的连接才能获得它。通过对Logs表引入一些外键
非规范化，我可以跳过所有连接：
ClientApplication has_many => ClientApplicationVersions
ClientApplication has_many => Logs
ClientApplicationVersions has_many => CloudLogs
ClientApplicationVersions has_many => Logs
CloudLogs has_many => Logs
最终的结果是，我的日志表中会有一些额外的列：client\u application\u key
，client\u application\u version\u key
，以及cloud\u log\u key
虽然我冒着数据不一致的风险，但我可以避免这里的3个连接，它们有助于降低查询的性能。请有人告诉我不要这样。试着回答你的每个问题：
当然可以！您正在搜索的任何内容都应该被编入索引。如果没有索引，则必须进行完整的表扫描。如果使用create_table
中的references
功能，则在执行初始迁移时创建的关联ID之上，您至少正在搜索以下内容：
- logs.timestamp
- 客户端\u应用程序\u版本.public\u密钥
- 客户端应用程序。公钥
- logs.deleted_在
这些可能都应该编入索引。当然，如果在定义关联外键时没有使用引用
，那么也可以添加它们。当然，与指数之间存在权衡。它们就像阅读的魔法，但它们可能会显著减慢你的写作速度。它们在多大程度上减慢或加快了您的速度，可能也严重依赖于数据库
我不这么认为。您的rails代码看起来与rig有关
ClientApplication.find_all_by_account_id(1).where(public_key: 'p0kZudG0').joins(:client_application_version).where("client_application_versions.public_key=?",'0HgoJRyE').logs.page(1)
SELECT
`logs`.*
FROM
`logs` as l
INNER JOIN `cloud_logs` as cl1
ON
cl1.id = l.cloud_log_id
INNER JOIN `cloud_logs` as cl2
ON
cl2.id = l.cloud_log_id
INNER JOIN `client_application_versions` as cav1
ON
cav1.id = cl1.client_application_version_id
INNER JOIN `client_application_versions` as cav2
ON
cav2.id = cl2.client_application_version_id
INNER JOIN `client_applications` as ca
ON
ca.id = cav1.client_application_id
WHERE
(l.deleted_at IS NULL)
AND
(ca.account_id = 1)
AND
(ca.public_key = 'p0kZudG0')
AND
(cav.public_key = '0HgoJRyE')
ORDER BY
logs.timestamp DESC
LIMIT
0, 100
SELECT
`logs`.*
FROM
`logs` as l
INNER JOIN `cloud_logs` as cl1
ON
cl1.id = l.cloud_log_id
-- INNER JOIN `cloud_logs` as cl2
-- ON
-- cl2.id = l.cloud_log_id
INNER JOIN `client_application_versions` as cav1 use index for join (`index_cavs_on_client_application_id_and_public_key`)
ON
cav1.id = cl1.client_application_version_id
AND
cav1.public_key = '0HgoJRyE'
-- INNER JOIN `client_application_versions` as cav2
-- ON
-- cav2.id = cl2.client_application_version_id
INNER JOIN `client_applications` as ca
ON
ca.id = cav1.client_application_id
WHERE
(l.deleted_at IS NULL)
AND
(ca.account_id = 1)
AND
(ca.public_key = 'p0kZudG0')
ORDER BY
logs.timestamp DESC
LIMIT
0, 100
Log.where(:deleted_at.ne => nil).order("logs.timestamp desc").joins(:cloud_logs) & \
CloudLog.joins(:client_application_versions) & \
ClientApplicationVersion.where(:public_key => '0HgoJRyE').joins(:client_applications) & \
ClientApplication.where(:public_key => 'p0kZudG0', :account_id => 1)
alter table client_application_versions add key (`client_application_id`, `public_key`);
YourObject.joins(:client_application).
where(ClientApplication.arel_table[:public_key].eq(client_application_key))