Question

我有一个模型，我用它来使用awesome_nested_set插件跟踪层次结构组织中的权限。我遇到了一个问题，当两个named_scope链接在一起时，正在创建重复INNER JOIN。

class Group < ActiveRecord::Base
  acts_as_nested_set
  has_many :memberships
  has_many :accounts, :through => :memberships
  has_many :authorizations
  has_many :users, :through => :authorizations
end

这两个named_scope位于Account模型中，用于按用户和群组过滤帐户：

named_scope :in_group, lambda { |id|
  group_ids = Group.find(id).self_and_descendants.collect(&:id)
  { :joins => :memberships, :conditions => ["memberships.group_id in (?)", group_ids] }
}

named_scope :for, lambda { |user|
  groups = user.authorizations.groups.collect(&:id) unless user.admin?
  user.admin ? {} : { :joins => :groups, :conditions => ["groups.id IN (?)", groups] }
}

这两个named_scope都需要加入memberships，但如果没有重复，他们不应该这样做吗？当它们被链接在一起时，mysql会出现以下错误：

Mysql::Error: Not unique table/alias: 'memberships': SELECT `accounts`.* FROM `accounts` INNER JOIN `memberships` ON accounts.id = memberships.account_id INNER JOIN `memberships` ON `accounts`.`id` = `memberships`.`account_id` INNER JOIN `groups` ON `groups`.`id` = `memberships`.`group_id` WHERE ((memberships.group_id in (54,94)) AND (groups.id IN (54,94)))  ORDER BY business_name, location_name LIMIT 0, 75

Answer 1

尝试将for named范围中的join语句更改为:joins => {:memberships => :groups}。我怀疑has_many通过关系可能会导致它。

为什么这些named_scope会导致重复的INNER JOIN？

1 个答案: