has_many关联状态检查执行N + 1个查询活动管理员

问题描述

模型结构：用户拥有许多订阅和博客，订阅具有has_many优惠券。
我已经包含has_many表，但是我需要为每个订阅执行状态检查
因此，如果我在范围集合中执行where查询，则它将使所有用户仅具有有效订阅。那么如何避免N + 1查询并执行状态检查。

Model Strucure: User has many subscriptions and blogs , Subscriptions has_many coupons.I have included the has_many table but i need to perform state check for every subscription So if i perform where query in scoped collection than it gets all the user only having valid subscriptions. So how to avoid N+1 query and also perform state check.

def scoped_collection
  end_of_association_chain.includes(:subscriptions, :blogs)
end
index do  
  column :email
  column "referrer" do |user|
    subscription = user.subscriptions.valid.first
    subscription.referrers.first.code if subscription
  end
  column "blog_id" do |user|
     user.blog.id if user.blog
  end

end

推荐答案

仅从查询中加载有效的订阅，请检查以下代码

Load valid subscriptions from query only, please check below code

 controller do
      def scoped_collection
        User.includes(subscriptions: :referrers).select("users.*, (SELECT referrers.code from referrers WHERE subscriptions.state = 1 LIMIT 1) as refer_code")
      end
  end

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