我怎么才能重构这个呢？同时也减少了对服务器的调用？

Question

我有这个方法。它的工作是返回一份已经毕业于开发商的学员名单。用户筛选他们在开发人员中寻找的技能。返回列表时，列表的顶部是更相关的开发人员。

这是控制器方法：

  def filter
    @skills = Skill.all
    @developers = []
    unless params[:ids].nil?
      params[:ids].each do |skill|
        skill = @skills.find(skill)
        skill.trainees.each do |developer|
          @developers << developer
        end
      end
    end
    if @developers.empty?
      @developers = Trainee.developers.all
    else
      @developers = @developers.group_by {|x| x}.map {|k, v| [k, v.count]}
      @developers.sort_by!(&:last).reverse!
      @developers.map! do |developer|
        developer[0]
      end
    end
    respond_to do |format|
      format.js {}
    end
  end

目前，相同的方法正在按我想要的次数访问服务器。下面的服务器日志显示的结果是我单击了11个要过滤的按钮。可以是1、5或20，这取决于用户所寻找的内容。

Processing by SkillsController#filter as */*
  Parameters: {"ids"=>["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"]}
  Skill Load (0.6ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 1 LIMIT 1
  Trainee Load (0.6ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 1
  Skill Load (0.4ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 2 LIMIT 1
  Trainee Load (0.6ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 2
  Skill Load (0.3ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 3 LIMIT 1
  Trainee Load (1.3ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 3
  Skill Load (6.1ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 4 LIMIT 1
  Trainee Load (0.6ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 4
  Skill Load (0.3ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 5 LIMIT 1
  Trainee Load (0.9ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 5
  Skill Load (2.6ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 6 LIMIT 1
  Trainee Load (2.0ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 6
  Skill Load (4.2ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 7 LIMIT 1
  Trainee Load (0.9ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 7
  Skill Load (1.2ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 8 LIMIT 1
  Trainee Load (3.0ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 8
  Skill Load (0.3ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 9 LIMIT 1
  Trainee Load (0.8ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 9
  Skill Load (2.1ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 10 LIMIT 1
  Trainee Load (0.6ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 10
  Skill Load (0.3ms)  SELECT  `skills`.* FROM `skills` WHERE `skills`.`id` = 11 LIMIT 1
  Trainee Load (0.8ms)  SELECT `trainees`.* FROM `trainees` INNER JOIN `mastered_skills` ON `trainees`.`id` = `mastered_skills`.`trainee_id` WHERE `mastered_skills`.`skill_id` = 11
  Rendering skills/filter.js.haml
  Skill Load (0.7ms)  SELECT `skills`.* FROM `skills` INNER JOIN `mastered_skills` ON `skills`.`id` = `mastered_skills`.`skill_id` WHERE `mastered_skills`.`trainee_id` = 5
  Skill Load (0.5ms)  SELECT `skills`.* FROM `skills` INNER JOIN `mastered_skills` ON `skills`.`id` = `mastered_skills`.`skill_id` WHERE `mastered_skills`.`trainee_id` = 2728
  Skill Load (0.6ms)  SELECT `skills`.* FROM `skills` INNER JOIN `mastered_skills` ON `skills`.`id` = `mastered_skills`.`skill_id` WHERE `mastered_skills`.`trainee_id` = 10

Answer 1

首先，@skills可以定义为：@skills = params[:ids].nil? ? Skill.all : Skills.where(id: params[:ids])

然后你就面临着n+1问题。为了避免这种情况，您必须使用殷切装载协会 (ELA)或联接。

若要返回带ELA的受训者对象，可以使用map和flatten。

接下来，你有一个很好的角色：

@developers = @developers.group_by {|x| x}.map {|k, v| [k, v.count]}
@developers.sort_by!(&:last).reverse!

sort_by(&:last).reverse工作得很快。

本部分：

@developers.map! do |developer|
  developer[0]
end

可改为：

@developers.map(&:first)

并与以前的sort_by联合

@developers = @developers.sort_by(&:last).reverse.map(&:first)

希望能帮上忙。

Answer 2

优化本部分：

@skills = Skill.all
@developers = []
unless params[:ids].nil?
  params[:ids].each do |skill|
    skill = @skills.find(skill)
    skill.trainees.each do |developer|
      @developers << developer
    end
  end
end

至：

@developers = Skill.where(id: params[:ids]).joins(:trainees).select('trainees.*')

Answer 3

所描述的问题看起来像一个N+1 problem。急切地加载关联可能会有所帮助：Querying.html#急切-加载-关联