我有以下查询。我们的想法是,它让我知道groups
以及随后users
可以访问每个component_instance
。我想知道是否有更好的方法来执行此操作,因为查询速度很慢,但每次处理此表时都有这些额外的列非常方便:
SELECT component_instances.*,
GROUP_CONCAT(DISTINCT IF(permissions.view, groups.id, NULL)) AS view_group_ids,
GROUP_CONCAT(DISTINCT IF(permissions.edit, groups.id, NULL)) AS edit_group_ids,
GROUP_CONCAT(DISTINCT IF(permissions.view, users.id, NULL)) AS view_user_ids,
GROUP_CONCAT(DISTINCT IF(permissions.edit, users.id, NULL)) AS edit_user_ids
FROM `component_instances`
LEFT OUTER JOIN permissions ON permissions.component_instance_id = component_instances.id
LEFT OUTER JOIN groups ON groups.id = permissions.group_id
LEFT OUTER JOIN groups_users ON groups_users.group_id = groups.id
LEFT OUTER JOIN users ON users.id = groups_users.user_id
GROUP BY component_instances.id
ORDER BY (case when component_instances.ancestry is null then 0 else 1 end), component_instances.ancestry, position
权限表就像这样(原谅Rails!):
create_table "permissions", :force => true do |t|
t.integer "component_instance_id"
t.integer "group_id"
t.boolean "view", :default => false
t.boolean "edit", :default => false
end
权限类型为edit
和view
。可以为一个组分配一个或两个。权限也是递归的,如果component_instance
上没有组权限,我们必须检查其祖先以找到设置权限的第一个(如果有)。这使得一个查询非常重要,因为我可以将此查询与ancestry
gem提供的选择逻辑(物化路径树)结合起来。
更新
我已经更快地找到了这个查询基准:
SELECT component_instances.*,
GROUP_CONCAT(DISTINCT view_groups.id) AS view_group_ids,
GROUP_CONCAT(DISTINCT edit_groups.id) AS edit_group_ids,
GROUP_CONCAT(DISTINCT view_users.id) AS view_user_ids,
GROUP_CONCAT(DISTINCT edit_users.id) AS edit_user_ids
FROM `component_instances`
LEFT OUTER JOIN permissions ON permissions.component_instance_id = component_instances.id
LEFT OUTER JOIN groups view_groups ON view_groups.id = permissions.group_id AND permissions.view = 1
LEFT OUTER JOIN groups edit_groups ON edit_groups.id = permissions.group_id AND permissions.edit = 1
LEFT OUTER JOIN groups_users view_groups_users ON view_groups_users.group_id = view_groups.id
LEFT OUTER JOIN groups_users edit_groups_users ON edit_groups_users.group_id = edit_groups.id
LEFT OUTER JOIN users view_users ON view_users.id = view_groups_users.user_id
LEFT OUTER JOIN users edit_users ON edit_users.id = edit_groups_users.user_id
GROUP BY component_instances.id
ORDER BY (case when component_instances.ancestry is null then 0 else 1 end), component_instances.ancestry, position
这是上面查询的EXPLAIN和表CREATE语句:
+----+-------------+---------------------+--------+-----------------------------------------------+--------------------------------------------+---------+--------------------------------------------+------+------------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------------+--------+-----------------------------------------------+--------------------------------------------+---------+--------------------------------------------+------+------------------------------------------------------+
| 1 | SIMPLE | component_instances | ALL | PRIMARY,index_component_instances_on_ancestry | NULL | NULL | NULL | 119 | "Using temporary; Using filesort" |
| 1 | SIMPLE | permissions | ALL | NULL | NULL | NULL | NULL | 6 | "Using where; Using join buffer (Block Nested Loop)" |
| 1 | SIMPLE | view_groups | eq_ref | PRIMARY | PRIMARY | 4 | 05707d890df9347c.permissions.group_id | 1 | "Using where; Using index" |
| 1 | SIMPLE | edit_groups | eq_ref | PRIMARY | PRIMARY | 4 | 05707d890df9347c.permissions.group_id | 1 | "Using where; Using index" |
| 1 | SIMPLE | view_groups_users | ref | index_groups_users_on_group_id_and_user_id | index_groups_users_on_group_id_and_user_id | 5 | 05707d890df9347c.view_groups.id | 1 | "Using index" |
| 1 | SIMPLE | edit_groups_users | ref | index_groups_users_on_group_id_and_user_id | index_groups_users_on_group_id_and_user_id | 5 | 05707d890df9347c.edit_groups.id | 1 | "Using index" |
| 1 | SIMPLE | view_users | eq_ref | PRIMARY | PRIMARY | 4 | 05707d890df9347c.view_groups_users.user_id | 1 | "Using index" |
| 1 | SIMPLE | edit_users | eq_ref | PRIMARY | PRIMARY | 4 | 05707d890df9347c.edit_groups_users.user_id | 1 | "Using index" |
+----+-------------+---------------------+--------+-----------------------------------------------+--------------------------------------------+---------+--------------------------------------------+------+------------------------------------------------------+
CREATE TABLE `component_instances` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`visible` int(11) DEFAULT '1',
`instance_id` int(11) DEFAULT NULL,
`deleted_on` date DEFAULT NULL,
`instance_type` varchar(255) DEFAULT NULL,
`component_id` int(11) DEFAULT NULL,
`deleted_root_item` int(11) DEFAULT NULL,
`locked_until` datetime DEFAULT NULL,
`theme_id` int(11) DEFAULT NULL,
`position` int(11) DEFAULT NULL,
`ancestry` varchar(255) DEFAULT NULL,
`ancestry_depth` int(11) DEFAULT '0',
`cached_name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `index_component_instances_on_ancestry` (`ancestry`)
) ENGINE=InnoDB AUTO_INCREMENT=121 DEFAULT CHARSET=utf8
CREATE TABLE `groups` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8
CREATE TABLE `groups_users` (
`group_id` int(11) DEFAULT NULL,
`user_id` int(11) DEFAULT NULL,
KEY `index_groups_users_on_group_id_and_user_id` (`group_id`,`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
CREATE TABLE `permissions` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`component_instance_id` int(11) DEFAULT NULL,
`group_id` int(11) DEFAULT NULL,
`view` tinyint(1) DEFAULT '0',
`edit` tinyint(1) DEFAULT '0',
PRIMARY KEY (`id`),
KEY `edit_permissions_index` (`edit`,`group_id`,`component_instance_id`),
KEY `view_permissions_index` (`view`,`group_id`,`component_instance_id`)
) ENGINE=InnoDB AUTO_INCREMENT=28 DEFAULT CHARSET=utf8
CREATE TABLE `users` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`real_name` varchar(255) DEFAULT NULL,
`username` varchar(255) NOT NULL DEFAULT '',
`email` varchar(255) NOT NULL DEFAULT '',
`crypted_password` varchar(255) DEFAULT NULL,
`administrator` int(11) NOT NULL DEFAULT '0',
`password_salt` varchar(255) DEFAULT NULL,
`remember_token_expires` datetime DEFAULT NULL,
`persistence_token` varchar(255) DEFAULT NULL,
`disabled` tinyint(1) DEFAULT NULL,
`time_zone` varchar(255) DEFAULT NULL,
`login_count` int(11) DEFAULT NULL,
`failed_login_count` int(11) DEFAULT NULL,
`last_request_at` datetime DEFAULT NULL,
`current_login_at` datetime DEFAULT NULL,
`last_login_at` datetime DEFAULT NULL,
`current_login_ip` varchar(255) DEFAULT NULL,
`last_login_ip` varchar(255) DEFAULT NULL,
`perishable_token` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`id`),
UNIQUE KEY `index_users_on_username` (`username`),
KEY `index_users_on_perishable_token` (`perishable_token`)
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8
ORDER BY
来自ancestry gem,但如果有更好的方法,我很乐意将其作为拉取请求提交给他们。
答案 0 :(得分:2)
如果我们没有您的表格结构和索引,那么几乎不可能优化您的查询。使用EXPLAIN
语句是查询优化的必要部分。
如果没有上述信息,我可以对您的问题发表评论的是,您的ORDER BY
部分可以从某些优化中获益。在条件中使用任何函数或语句将始终导致灾难。同样使用ORDER BY
中的可空字段也会导致问题。也许最简单的方法是在表中添加一个新字段,保存0和1而不是当前的CASE
语句。
不要忘记,如果记录数量相当大,那么在/ group by的条件/顺序中的任何字段上都有索引。
<强> [UPDATE] 强>
您的查询非常简单。 EXPLAIN
的结果显示,唯一适合作为索引候选者的部分是:
CREATE INDEX inx4 ON permissions (`component_instance_id`, `group_id`, `edit`, `view`);
EXPLAIN
的第二行显示您的查询中没有表permissions
的索引。这是因为MySQL在使用索引时有几条规则:
考虑到您的查询以及提及表permissions
的所有四个字段这一事实,您需要对所有这四个字段进行索引,否则它将无用。
然而ORDER BY
可以从我之前提到的修正案中受益。
答案 1 :(得分:1)
NULL
(可以使用COALESCE
将NULL
替换为其他内容,而不是使用其他排序列。第二件事是减少连接,因为最后两个是在我们连接的id上。
SELECT
component_instances.*,
GROUP_CONCAT(DISTINCT view_groups.id) AS view_group_ids,
GROUP_CONCAT(DISTINCT edit_groups.id) AS edit_group_ids,
GROUP_CONCAT(DISTINCT view_groups_users.user_id) AS view_user_ids,
GROUP_CONCAT(DISTINCT edit_groups_users.user_id) AS edit_user_ids
FROM
`component_instances`
LEFT OUTER JOIN permissions
ON permissions.component_instance_id = component_instances.id
LEFT OUTER JOIN groups view_groups
ON view_groups.id = permissions.group_id AND permissions.view = 1
LEFT OUTER JOIN groups edit_groups
ON edit_groups.id = permissions.group_id AND permissions.edit = 1
LEFT OUTER JOIN groups_users view_groups_users
ON view_groups_users.group_id = view_groups.id
LEFT OUTER JOIN groups_users edit_groups_users
ON edit_groups_users.group_id = edit_groups.id
GROUP BY
component_instances.id
ORDER BY
component_instances.ancestry, -- MySQL was sorting the NULL values already correctly
position
;