活動記錄查詢與用戶範圍

Question

所以我想優化我的ActiveRecord查詢做更有效的事情。目前，當我查詢使用遵循我的方法得到類似如下：

SELECT "expirations".* FROM "expirations" WHERE (user_id = 14 and expire_on <= '2014-09-25') 
SELECT "expirations".* FROM "expirations" WHERE (user_id = 15 and expire_on <= '2014-09-25') 
SELECT "expirations".* FROM "expirations" WHERE (user_id = 17 and expire_on <= '2014-09-25') 

等等，直到所有用戶的查詢完成。什麼會更有效率，我想要達到的是類似於以下內容：

SELECT "expirations".* FROM "expirations" WHERE (user_id IN (14,15,17) and expire_on <= '2014-09-25') 

有意義嗎？我不知道如何去做這件事，所以一些方向將是特殊的！

def expired_trainings(current_user) 
    retval = [] 
    Organization.appropriate_users(current_user).each do |user| 
     Expiration.where("user_id = #{user.id} and expire_on <= '#{Date.today}'").each do |expir| 
     retval << expir 
     end 
    end 
    ttypes = [] 
    if current_user.max_role.downcase == 'leader' 
     current_user.leading_groups.each do |g| 
     g.training_types.each do |tt| 
      ttypes << tt 
     end 
     end 
     ttypes.flatten.uniq! 
     retval.delete_if { |expir| !ttypes.include?(expir.training_type) } 
    end 
    retval.flatten 
    end 

Answer 1

可以簡化（優化）此塊：

retval = [] 
Organization.appropriate_users(current_user).each do |user| 
    Expiration.where("user_id = #{user.id} and expire_on <= '#{Date.today}'").each do |expir| 
    retval << expir 
    end 
end 

下到這一點：

appropriate_users = Organization.appropriate_users(current_user) 
retval = Expiration.where(user_id: appropriate_users).where(['expire_on <= ?', Date.today]) 

這將在一個查詢中檢索所有的appropriate_users的到期時間。