rails tutorial のカレントユーザーのキャッシュについて

Question

rails tutorial　のセッションヘルパーでおそらく一番重要なcurrent_user

  def current_user
    if (user_id = session[:user_id])
      @current_user ||= User.find_by(id: user_id)
    elsif (user_id = cookies.signed[:user_id])
      user = User.find_by(id: user_id)
      if user && user.authenticated?(:remember, cookies[:remember_token])
        log_in user
        @current_user = user
      end
    end
  end

で@current_user ||= .......
のように書くと一度current_userすればメモリに保存してその後は再度クエリを発行しないということだったと思うのですが、ログを見てみるとnewやindexにいくたびにクエリを発行しています。

Started GET "/users/new" for ::1 at 2019-11-03 18:23:11 +0900
Processing by UsersController#new as HTML
  Rendering users/new.html.erb within layouts/application
  Rendered shared/_error_messages.html.erb (Duration: 0.2ms | Allocations: 21)
  Rendered users/_form.html.erb (Duration: 30.8ms | Allocations: 927)
  Rendered users/new.html.erb within layouts/application (Duration: 33.5ms | Allocations: 1310)
  User Load (0.3ms)  SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2  [["id", "ca89455c-a092-497f-b3dd-9744f6dd852f"], ["LIMIT", 1]]⬅️ここ
  ↳ app/helpers/sessions_helper.rb:8:in `current_user'
  Rendered layouts/_deviation_common.html.erb (Duration: 1.9ms | Allocations: 728)
  Rendered layouts/_deviation_footer.html.erb (Duration: 0.2ms | Allocations: 71)
Completed 200 OK in 59ms (Views: 58.1ms | ActiveRecord: 0.3ms | Allocations: 5489)


Started GET "/users" for ::1 at 2019-11-03 18:23:12 +0900
Processing by UsersController#index as HTML
  **User Load (0.5ms)  SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2  [["id", "ca89455c-a092-497f-b3dd-9744f6dd852f"], ["LIMIT", 1]]**⬅️ここ
  ↳ app/helpers/sessions_helper.rb:8:in `current_user'
  Rendering users/index.html.erb within layouts/application
  User Load (41.7ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" DESC
  ↳ app/views/users/index.html.erb:3
  Rendered collection of users/_user.html.erb [2 times] (Duration: 1.5ms | Allocations: 357)
  Rendered users/index.html.erb within layouts/application (Duration: 46.0ms | Allocations: 1433)
  Rendered layouts/_deviation_common.html.erb (Duration: 0.3ms | Allocations: 116)
  Rendered layouts/_deviation_footer.html.erb (Duration: 0.1ms | Allocations: 71)
Completed 200 OK in 70ms (Views: 25.3ms | ActiveRecord: 42.3ms | Allocations: 5583)

スコープが有効でないのかなと思ったのでグローバル変数にしてみたところちゃんと最初の一回だけになりました。

  def current_user
    if (user_id = session[:user_id])
      $current_user ||= User.find_by(id: user_id) ⬅️ここ
    elsif (user_id = cookies.signed[:user_id])
      user = User.find_by(id: user_id)
      if user && user.authenticated?(:remember, cookies[:remember_token])
        log_in user
        $current_user = user
      end
    end
  end

Started GET "/users/new" for ::1 at 2019-11-03 18:34:21 +0900
Processing by UsersController#new as HTML
  Rendering users/new.html.erb within layouts/application
  Rendered shared/_error_messages.html.erb (Duration: 0.1ms | Allocations: 21)
  Rendered users/_form.html.erb (Duration: 1.0ms | Allocations: 557)
  Rendered users/new.html.erb within layouts/application (Duration: 1.3ms | Allocations: 663)
  Rendered layouts/_deviation_common.html.erb (Duration: 0.4ms | Allocations: 107)
  Rendered layouts/_deviation_footer.html.erb (Duration: 0.2ms | Allocations: 68)
Completed 200 OK in 17ms (Views: 16.0ms | ActiveRecord: 0.0ms | Allocations: 4067)


Started GET "/users" for ::1 at 2019-11-03 18:34:56 +0900
Processing by UsersController#index as HTML
  Rendering users/index.html.erb within layouts/application
  User Load (0.5ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" DESC
  ↳ app/views/users/index.html.erb:3
  Rendered collection of users/_user.html.erb [2 times] (Duration: 0.8ms | Allocations: 208)
  Rendered users/index.html.erb within layouts/application (Duration: 3.6ms | Allocations: 1012)
  Rendered layouts/_deviation_common.html.erb (Duration: 0.4ms | Allocations: 108)
  Rendered layouts/_deviation_footer.html.erb (Duration: 0.2ms | Allocations: 68)
Completed 200 OK in 23ms (Views: 20.8ms | ActiveRecord: 0.5ms | Allocations: 4450)

@でなくて$を使った方が正解なのでしょうか？
なにか勘違いしているところあったら教えてください。

rails6.0.0 ruby 2.6.3

Answer 1

@にしてください。
＄にすると誰がloginしても最初にloginした人のアカウントのままになってしまいます

＞一度current_userすればメモリに保存してその後は再度クエリを発行しないということだったと思うのですが、
そのとおりです、ですがその有効範囲・期間は そのリクエスト完了までです。

＞ログを見てみるとnewやindexにいくたびにクエリを発行しています。
これも正しい動作です。

＠のスコープはそのインスタンスです。
GETやPOSTのたびにControllerの新しいインスタンスが作られるので、その都度クエリが必要です

Comments

[shumbow]

ありがとうございます！またお願いします！