Rails アプリの 5,000 件の N+1 問題と戦っている話

川原 万季 @makicamel
2023 年 10 月 27 日
Kaigi on Rails 2023
話者の勤める会社のとある歴史あるリポジトリでは CI で約 5,000 件の N+1 問題が検知されていました。 N+1 問題はパフォーマンス劣化の代表的な要因のひとつです。 Rails にはこれを解決する includes というメソッドがあり、これを警告する Bullet という gem があります。 Bullet の警告箇所に includes を差し込めばよさそうですが、5,000 件の手修正は億劫なので実行時に N+1 クエリ発行箇所に includes を差し込む gem を作りました。

しかし現実のアプリケーションは複雑で、単純に includes すればよいというものではありません。 例えば以下のコードは alias が重複しエラーになります。

Play.joins(:actors).includes(actors: :company).joins('INNER JOIN companies force index(primary) ON companies.id = actors.company_id').load

エラーにならなくとも不要な includes はパフォーマンス劣化を招きます。 こうした意図しない変更を避けて includes を差し込む必要があります。

本セッションでは作った gem の解説と、この gem による修正をリリースする話をします。

Transcript

1. Rails
   ΞϓϦͷ 
 5,000
   ݅ͷ
   N+1
   ໰୊ͱ 
 ઓ͍ͬͯΔ࿩ 2023.10.27. Kaigi on Rails 2023 @makicamel
2. ͓࿳ͼ
4. ͳ͗౗ͤ 
 ·ͤΜͰͨ͠ 💧
5. ͓Εͨͪͷઓ͍͸ 
 ͔͜͜Βͩ
6. Rails
   ΞϓϦͷ 
 5,000
   ݅ͷ
   N+1
   ໰୊ͱ 
 ઓ͍ͬͯΔ࿩
7. ࣗݾ঺հ w!NBLJDBNFM
   
   ઒ݪສق
   w3VCZ
   
   
   
   
   
   ͱϏʔϧɹɹͱ͓ञ͕޷͖
   w޷͖ͳ
   73
   ήʔϜ
   w
   
   
8. N+1 ໰୊ 
 ͋Γ·͔͢ʁ
9. N+1 ໰୊
 Կ݅͋Γ·͔͢ʁ
10. N+1 ໰୊ͱ͸ ͔ΜͨΜͳ 
 ͓͞Β͍ ͔ΜͨΜͳ 
 આ໌༻Ϟσϧ
11. 
    plays = Play.limit(10) plays.each do |play| puts play.actors.map(&:name) end
    SELECT "plays".* FROM "plays" LIMIT 10 SELECT "actors".* FROM "actors" INNER JOIN "play_actors" ON "actors"."id" = "play_actors"."actor_id" WHERE "play_actors"."play_id" = 1 SELECT "actors".* FROM "actors" INNER JOIN "play_actors" ON "actors"."id" = "play_actors"."actor_id" WHERE "play_actors"."play_id" = 2 
 SELECT "actors".* FROM "actors" INNER JOIN "play_actors" ON "actors"."id" = "play_actors"."actor_id" WHERE "play_actors"."play_id" = 3 
 ... 10 + 1 ճͷΫΤϦ͕ൃߦ͞ΕΔ N+1 ໰୊ͱ͸
12. N+1 ໰୊ରࡦ •ActiveRecord::QueryMethods#preload •ActiveRecord::QueryMethods#eager_load •ActiveRecord::QueryMethods#includes Rails ฤ 🛤
13. ActiveRecord::QueryMethods#preload
    plays = Play.preload(:actors).limit(10) plays.each do |play| puts play.actors.map(&:name) end
    SELECT "plays".* FROM "plays" LIMIT 10 SELECT "play_actors".* FROM "play_actors" WHERE "play_actors"."play_id" IN (1, 2, 3, ...) SELECT "actors".* FROM "actors" WHERE "actors"."id" IN (1, 2, 3, ...) 3 ͭʹ෼͚ΒΕͨΫΤϦ͕ൃߦ͞ΕΔ
14. ActiveRecord::QueryMethods#eager_load
    plays = Play.eager_load(:actors).limit(10) plays.each do |play| puts play.actors.map(&:name) end
    SELECT DISTINCT "plays"."id" FROM "plays" LEFT OUTER JOIN "play_actors" ON "play_actors"."play_id" = "plays"."id" LEFT OUTER JOIN "actors" ON "actors"."id" = "play_actors"."actor_id" LIMIT 10 SELECT "plays"."id" AS t0_r0, ... FROM "plays" LEFT OUTER JOIN "play_actors" ON "play_actors"."play_id" = "plays"."id" LEFT OUTER JOIN "actors" ON "actors"."id" = "play_actors"."actor_id" WHERE "plays"."id" IN (1, 2, 3, ...) LEFT OUTER JOIN ͨ͠ 
 ΫΤϦ͕ൃߦ͞ΕΔ
15. ActiveRecord::QueryMethods#includes
16. ActiveRecord::QueryMethods#includes ActiveRecord::QueryMethods#includes
 https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-includes
 ೔ຊޠ͸ൃදऀ༁ Specify associations args to be eager loaded to prevent N + 1 queries. 
 A separate query is performed for each association, 
 unless a join is required by conditions. N + 1 ΫΤϦΛ๷͙ͨΊʹ args associations Λ eager_load ͢ΔΑ͏ࢦఆ͠·͢ɻ 
 ৚݅ʹΑͬͯ join ͕ඞཁͰͳ͚Ε͹ɺ 
 ֤ association ͝ͱʹݸผͷΫΤϦ͕࣮ߦ͞Ε·͢ɻ
17. ActiveRecord::QueryMethods#includes ActiveRecordͷjoinsͱpreloadͱincludesͱeager_loadͷҧ͍ / @k0kubun
 https://qiita.com/k0kubun/items/80c5a5494f53bb88dc58 •includes ͨ͠ςʔϒϧͰ where ʹΑΔߜΓࠐΈΛߦ͍ͬͯΔ •includes ͨ͠ association ʹରͯ͠ joins ͔ references ΋ݺΜͰ͍Δ •೚ҙͷ association ʹରͯ͠ eager_load ΋ݺΜͰ͍Δ ͷ͏͍ͪͣΕ͔Λຬͨ͢৔߹ɺeager_load ͱಉ͡ڍಈ(LEFT JOIN)Λߦ͍ɺ 
 ͦ͏Ͱͳ͚Ε͹ preload ͱಉ͡ڍಈ(ΫΤϦΛ෼͚࣮ͯߦ)Λ͢Δɻ 
 ߜΓࠐΈ͕ඞཁͳ࣌ʹྫ֎Λ౤͛ͣ eager_load ʹfallback͢Δ preloadɻ
18. N+1 ໰୊ରࡦ gem ฤ 💎
19. Bullet 🔫
20. fl yerhzm / bullet
 https://github.com/ fl yerhzm/bullet Bullet 🔫 ɹN+1 ΍ෆཁͳ eager_loadingͳͲΛ 
 ɹϩά΍ը໘ʹදࣔͯ͠ڭ͑ͯ͘ΕΔ
21. 
    # config/environments/test.rb Rails.application.configure do config.after_initialize do Bullet.enable = true Bullet.raise = true end end Bullet 🔫 ɹraise Λࢦఆ͢ΔͱΤϥʔΛى͜͢
22. N+1 ໰୊
 Կ݅͋Γ·͔͢ʁ ʢ࠶ܝʣ
23. ※ unused eager_loading ͱ counter cache ͷ਺΋ؚΈ·͢
24. 4722 tests failed
25. ߕຊҰ / Ϛογϡϧ-MASHLE-
 https://mashle.pw
26. ͭͬͨ͘ 🩹 makicamel / bulletmark_repairer
 https://github.com/makicamel/bulletmark_repairer
27. ͭͬͨ͘ 🩹 makicamel / bulletmark_repairer
 https://github.com/makicamel/bulletmark_repairer
28. 
    BulletmarkRepairer 🩹 class PlaysController < ApplicationController def index @plays = Play.all end end
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> N+1 ൃੜ
29. 
    BulletmarkRepairer 🩹 class PlaysController < ApplicationController def index @plays = Play.all end end
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> N+1 ൃੜ
    $ REPAIR=1 rspec
30. 
    BulletmarkRepairer 🩹 class PlaysController < ApplicationController def index @plays = Play.all.includes([:actors]) end end
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> ɹ࣮ߦ࣌ʹ autocorrect Ͱ 
 ɹincludes Λ௥Ճ͢Δ
    $ REPAIR=1 rspec
31. BulletmarkRepairer ͷ 
 ͭ͘Γํ 🛠
32. ྩ࿨ͷ࣌୅ʹ 
 खͰ includes ॻ͘ͷ 
 ໘౗͍͘͞
33. Bullet ͕ N+1 Λݕ஌ͨ͠Β 
 includes Λఴ෇ͨ͠Β 
 ͍͍Μ͡Όͳ͍ʁ
34. •Ͳ͜Ͱ includes ͢Δ΂͖͔ •ͳʹΛ includes ͢Δ΂͖͔ ໰୊
35. •Ͳ͜Ͱ includes ͢Δ΂͖͔ •ͳʹΛ includes ͢Δ΂͖͔ ໰୊
36. 
    Case 1. class PlaysController < ApplicationController def index @plays = Play.all end end
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> ɹϏϡʔͰ N+1 ͕ 
 ɹൃੜ͢Δέʔε
37. 
    Case 1. class PlaysController < ApplicationController def index @plays = Play.all end end
    <% @plays.includes(:actors).each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> ɹϏϡʔͰ 
 ɹincludes ͨ͘͠ͳ͍ 🙅
38. 
    Case 1. class PlaysController < ApplicationController def index @plays = Play.all.includes(:actors) end end
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> ɹίϯτϩʔϥͰ 
 ɹincludes ͍ͨ͠ 🙆
39. 
    Case 2. class PlaysController < ApplicationController def index plays = Play.all.map do |play| { title: play.name, actors: play.actors.map(&:name) } end render json: { data: plays } end end ɹίϯτϩʔϥͰ 
 ɹൃੜ͢Δέʔε
40. 
    Case 2. class PlaysController < ApplicationController def index plays = Play.all.includes(:actors).map do |play| { title: play.name, actors: play.actors.map(&:name) } end render json: { data: plays } end end ɹίϯτϩʔϥͰ 
 ɹ௚͢ͱΑͦ͞͏ 🙆
41. 
    Case 3. class PlaysController < ApplicationController before_action :set_plays def index render json: { data: @plays.as_json } end private def set_plays @plays = Play.all end end ɹίʔϧόοΫͰ 
 ɹActiveRecord Λ 
 ɹ૊ΈཱͯΔέʔε
42. 
    Case 3. class PlaysController < ApplicationController before_action :set_plays def index render json: { data: @plays.as_json } end private def set_plays @plays = Play.all.includes(:actors) end end ɹ͜ͷ৔߹͸ 
 ɹίʔϧόοΫͰ௚ͯ͠ 
 ɹΑͦ͞͏ 🙆
43. 
    Case 4. class PlaysController < ApplicationController def index render json: { data: scope.as_json } end def show render json: { data: scope.find(params[:id]).as_json } end private def scope Play.where('name like ?', params[:name]) end end ɹڞ௨ͷείʔϓΛ 
 ɹ࢖͍ͬͯΔ৔߹
44. 
    Case 4. class PlaysController < ApplicationController def index render json: { data: scope.as_json } end def show render json: { data: scope.find(params[:id]).as_json } end private def scope Play.where('name like ?', params[:name]) end end ɹΞΫγϣϯͰ 
 ɹ௚͢΂͖…ʁ🤔 ɹ͜ͷ͘Β͍ͳΒ 
 ɹείʔϓͰ௚ͯ͠΋ 
 ɹΑͦ͞͏͚ͩͲ…🤔 ɹshow Ͱ includes ͢Δ 
 ɹඞཁͳ͘ͳ͍ʁ🤔
45. 
    Case 5. ɹίϯτϩʔϥ͔Β 
 ɹݺͼग़ͨ͠ 
 ɹϞσϧͷϝιουͰ 
 ɹN+1 ͕ൃੜ͢Δέʔε class PlaysController < ApplicationController def index plays = Play.all render json: { data: plays.map(&:as_json_with_actors) } end end class Play < ApplicationRecord def as_json_with_actors as_json.merge(actors: actors.map(&:name)) end end
46. 
    Case 5. class PlaysController < ApplicationController def index plays = Play.all.includes(:actors) render json: { data: plays.map(&:as_json_with_actors) } end end class Play < ApplicationRecord def as_json_with_actors as_json.merge(actors: actors.map(&:name)) end end ɹίϯτϩʔϥͰ 
 ɹ௚͢ͱΑͦ͞͏ 🙆
47. 
    Case 6. ɹϞσϧͷίʔϧόοΫͰ 
 ɹΫΤϦ͠௚্ͨ͠Ͱ 
 ɹൃੜ͍ͯ͠Δέʔε class Play < ApplicationRecord after_save :notify_actors, if: :notification_required? private def notify_actors actors.where(...).each(&:notify!) end end
48. 
    Case 6. class Play < ApplicationRecord after_save :notify_actors, if: :notification_required? private def notify_actors actors.where(...).includes(:actors).each(&:notify!) end end ɹϞσϧͰ 
 ɹ௚͢ͱΑͦ͞͏ʁ
49. 
    Case 7. class TransitionPastPlaysService def initialize(border_date) @border_date = border_date end def execute plays = Play.where(created_at: ..@border_date) play_actors = plays.map do |play| { play_id: play.id, actor_id: play.actors.map(&:id) } end PastPlay.insert_all plays.map(&:as_json) PastPlayActor.insert_all play_actors plays.destroy_all end end ɹαʔϏε಺Ͱ 
 ɹPlay.where ্ͨ͠Ͱ 
 ɹൃੜ͢Δέʔε ※ ຊདྷ map(&:id) Ͱ͸ͳ͘ pluck(:id) ΍ ids Λ࢖͑͹ N+1 ͷӨڹ͸খ͘͞ͳΓ·͢
50. 
    Case 7. class TransitionPastPlaysService def initialize(border_date) @border_date = border_date end def execute plays = Play.where(created_at: ..@border_date).includes(:actors) play_actors = plays.map do |play| { play_id: play.id, actor_id: play.actors.map(&:id) } end PastPlay.insert_all plays.map(&:as_json) PastPlayActor.insert_all play_actors plays.destroy_all end end ※ ຊདྷ map(&:id) Ͱ͸ͳ͘ pluck(:id) ΍ ids Λ࢖͑͹ N+1 ͷӨڹ͸খ͘͞ͳΓ·͢ ɹαʔϏε಺Ͱ 
 ɹ௚͔͢͠ͳ͍
51. ۚాҰগ೥ͷࣄ݅฽֎఻ ൜ਓͨͪͷࣄ݅฽
 ఱथ੐ؙݪҊ ધ௡ਈฏݪҊ ͞ͱ͏;Έ΍ݪҊ ۚ੒ཅࡾ࿠ອը ߟ 
 ͑ 
 Δ ߟ 
 ͑ 
 Δ
52. •ίϯτϩʔϥͰ includes ͢Δͷ͸ਖ਼ͦ͠͏ •ෳ਺ͷΞΫγϣϯͰڞ௨είʔϓΛར༻͍ͯ͠Δ৔߹͸ʁ •ϏϡʔͰ includes ͢Δͷ͸޷·͘͠ͳͦ͞͏ •ϞσϧͷΠϯελϯεϝιουΑΓ΋ίϯτϩʔϥͰ includes͍ͨ͠ •ϝιου಺ͰΫΤϦ͠௚͍ͯ͠Δ৔߹͸ʁ •αʔϏεΫϥε etc … Ͳ͜Ͱ includes ͢Δ΂͖͔
53. Ϝζ͍ 😇
54. ;ͩΜ 
 Ͳ͏ͯ͠Δ͚ͬʁ
55. •جຊతʹίϯτϩʔϥͰ includes ͢Δ •ϓϥΠϕʔτϝιουΑΓΞΫγϣϯͰ includes ͢Δ͜ͱ͕ଟ͍ •ActiveRecord ͷ૊ΈཱͯॳظͰ includes ͢Δ͜ͱ͕ଟ͍ •΍ΉΛಘͳ͚Ε͹ϞσϧɾαʔϏεΫϥε etc Ͱ includes ͢Δ ;ͩΜͷࢥߟճ࿏
56. ;ͩΜͷࢥߟճ࿏
57. ;ͩΜͷࢥߟճ࿏
58. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
59. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end ɹBullet ͷϩά
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’
60. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹελοΫτϨʔεʹ 
 ɹίϯτϩʔϥ͕ͳ͍
61. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹमਖ਼͍ͨ͠ϑΝΠϧ͸ 
 ɹͬͪ͜ ɹελοΫτϨʔεʹ 
 ɹίϯτϩʔϥ͕ͳ͍
62. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹϏϡʔͰ N+1 Λൃੜͤ͞Δ஋͸ 
 ɹଟ͘ͷ৔߹Πϯελϯεม਺ʹೖ͍ͬͯΔ
63. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹN+1 ൃੜߦ͸Θ͔Δ
64. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹର৅ͬΆ͍ 
 ɹΠϯελϯεม਺͕Θ͔Δʢצʣ
65. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹURL ͕Θ͔Δ
66. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹίϯτϩʔϥͱ 
 ɹΞΫγϣϯ͕Θ͔Δ
67. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹΠϯελϯεม਺ʹ 
 ɹ୅ೖ͢Δͱ͜Ζʹ
68. Ϗϡʔฤ
    
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> class PlaysController < ApplicationController def index @plays = Play.all.includes(:actors) end end
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:2:in `block in _app_views_plays 
 _index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/ 
 index.html.erb:1:in `_app_views_plays 
 _index_html_erb__3206924200111145907_11500’ ɹincludes Λ଍͢✌
69. Ϗϡʔฤ
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <% if @favorite %> <%= actor.name %> <% end %> <% end %> <% end %> ର৅ͷΠϯελϯεม਺͸ 
 צͰ୳͍ͯ͠ΔͷͰ 
 ͜Μͳίʔυͩͱಈ͔ͳ͍ N+1 ൃੜՕॴ Πϯελϯεม਺Ά͍ 
 จࣈྻͦͷ 1ʢμ΢τʣ Πϯελϯεม਺Ά͍ 
 จࣈྻͦͷ 2ʢຊ෺ʣ
70. Ϗϡʔฤ
    <% Play.all.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %> Πϯελϯεม਺Λ 
 લఏͱ͍ͯ͠ΔͷͰ 
 ͜Μͳίʔυ΋ಈ͔ͳ͍
71. Ϗϡʔฤ
72. ;ͩΜͷࢥߟճ࿏
73. ίϯτϩʔϥฤ •͍͔ͭ͘ύλʔϯ͕͋Γͦ͏
74. ίϯτϩʔϥฤ
    class PlaysController < ApplicationController def index plays = Play.all.map do |play| { title: play.name, actors: play.actors.map(&:name) } end render json: { data: plays } end end ɹ͜͜Ͱ includes ͢Δͱ 
 ɹΑͦ͞͏
75. ίϯτϩʔϥฤ
    class PlaysController < ApplicationController def index @plays = scope if params[:future] @plays = @plays.where(performed_at: Date.today..) end gon.as_json = @plays.as_json end def show @play = scope.find(params[:id]) end private def scope Actor.find(params[:actor_id]).plays end end ɹ͜͜Ͱ includes ͢Δͱ 
 ɹΑͦ͞͏
76. ίϯτϩʔϥฤ
    class PlaysController < ApplicationController before_action :set_plays def index render json: { data: @plays.as_json } end private def set_plays @plays = Play.all end end ɹ͜͜Ͱ includes ͢Δͱ 
 ɹΑͦ͞͏ʁ
77. ίϯτϩʔϥฤ
78. ίϯτϩʔϥฤ ɹ͍ͬͨΜ 
 ɹޙճ͠
79. ίϯτϩʔϥฤ ɹϩά͔ΒURL ͕Θ͔ΔͷͰ 
 ɹίϯτϩʔϥͱ 
 ɹΞΫγϣϯ͕Θ͔Δ
80. ίϯτϩʔϥฤ
    class PlaysController < ApplicationController def index @plays = scope if params[:future] @plays = @plays.where(performed_at: Date.today..) end gon.as_json = @plays.as_json end def show @play = scope.find(params[:id]) end private def scope Actor.find(params[:actor_id]).plays end end ɹͻͱͭͷϝιου಺Ͱ 
 ɹෳ਺ճ୅ೖ͞Ε͍ͯΔ৔߹ 
 ɹͲͪΒ͕ਖ਼͍͔͠ 
 ɹػձతͳ൑ఆ͸ແཧ
81. ίϯτϩʔϥฤ
    class PlaysController < ApplicationController def index @plays = scope if params[:future] @plays = @plays.where(performed_at: Date.today..) end gon.as_json = @plays.as_json end def show @play = scope.find(params[:id]) end private def scope Actor.find(params[:actor_id]).plays end end ɹ࠷ॳʹ୅ೖ͢Δ΄͏͕ 
 ɹϢʔεέʔεͱͯ͠ଟͦ͏
82. ίϯτϩʔϥฤ ɹ࠶ؼతʹϝιουΛνΣοΫ 
 ɹݟ͔ͭΒͳ͚Ε͹ 
 ɹίʔϧόοΫΛνΣοΫ
83. ର৅ͷΠϯελϯεม਺͸ 
 Ϗϡʔಉ༷ 
 צͰ୳ͯ͠·͢ ίϯτϩʔϥฤ
84. ;ͩΜͷࢥߟճ࿏
85. ͦͷଞฤ ɹBullet ͷϩά͔Β 
 ɹൃੜߦ͕Θ͔ΔͷͰ 
 ɹͦ͜Ͱमਖ਼
86. ίϯτϩʔϥฤ ɹ͜ͷέʔε΋ 
 ɹճऩ
87. •Ͳ͜Ͱ includes ͢Δ΂͖͔ ✓ •ͳʹΛ includes ͢Δ΂͖͔ ໰୊
88. •Ͳ͜Ͱ includes ͢Δ΂͖͔ ✓ •ͳʹΛ includes ͢Δ΂͖͔ ໰୊
89. 
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.name %> <% end %> <% end %>
    <% @plays.each do |play| %> <% play.actors.each do |actor| %> <%= actor.company.name %> <% end %> <% end %> ɹ͜Μͳײ͡ͷϏϡʔ͕ 
 ɹ͋Δͱ͢Δ
90. Case 1.
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__3206924200111145907_11500'
    class PlaysController < ApplicationController def index @plays = Play.all end end ɹجຊέʔε
91. 
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__3206924200111145907_11500' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__3206924200111145907_11500'
    class PlaysController < ApplicationController def index @plays = Play.all.includes(:actors) end end Case 1. ɹجຊέʔε
92. Case 2.
    class PlaysController < ApplicationController def index @plays = Play.all end end ɹassociations ͕ 
 ɹෳ਺͋Δέʔε
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) 2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:theaters] Add to your query: .includes([:theaters])
93. 
    class PlaysController < ApplicationController def index @plays = Play.all.includes([:actors, :theaters]) end end Case 2. ɹassociations ͕ 
 ɹෳ਺͋Δέʔε
    2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) 2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:theaters] Add to your query: .includes([:theaters])
94. Case 3.
    2023-10-26 14:37:36[WARN] user: makicamel GET /plays USE eager loading detected Play => [{:actors=>[:company]}] Add to your query: .includes([:"{:actors=>[:company]}"]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__1665884924136242781_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_plays_index_html_erb__1665884924136242781_11760'
    class PlaysController < ApplicationController def index @plays = Play.all end end ɹωετ͍ͯ͠Δέʔε
95. Case 3.
    2023-10-26 14:37:36[WARN] user: makicamel GET /plays USE eager loading detected Play => [{:actors=>[:company]}] Add to your query: .includes([:"{:actors=>[:company]}"]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__1665884924136242781_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_plays_index_html_erb__1665884924136242781_11760'
    class PlaysController < ApplicationController def index @plays = Play.all.includes([{:actors=>[:company]}]) end end ɹωετ͍ͯ͠Δέʔε
96. 
    Case 4.
    2023-10-26 14:57:19[WARN] user: makicamel GET /plays USE eager loading detected Play => [:awesome_actors] Add to your query: .includes([:awesome_actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_html_erb___4265071383862059390_11760’ /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb___4265071383862059390_11760' class PlaysController < ApplicationController def index @plays = Play.all end end ɹωετ͍ͯ͠Δ͔ͭ 
 ɹassociation ʹผ໊͕͋Δέʔε
    class Play < ApplicationRecord has_many :play_actors has_many :awesome_actors, through: :play_actors, source: :actor end
97. 
    
    class PlaysController < ApplicationController def index @plays = Play.all.includes({:awesome_actors=>[:company]}) end end Case 4. 2023-10-26 14:57:19[WARN] user: makicamel GET /plays USE eager loading detected Play => [:awesome_actors] Add to your query: .includes([:awesome_actors]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_html_erb___4265071383862059390_11760’ /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb___4265071383862059390_11760' ɹωετ͍ͯ͠Δ͔ͭ 
 ɹassociation ʹผ໊͕͋Δέʔε
    class Play < ApplicationRecord has_many :play_actors has_many :awesome_actors, through: :play_actors, source: :actor end
98. 
    Case 5.
    2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' class PlaysController < ApplicationController def index @plays = Play.includes(:actors) end end ɹҰ෦ includes ࡁͷέʔε
99. 
    Case 5.
    2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' class PlaysController < ApplicationController def index @plays = Play.includes(:actors).includes({:actors=>[:company]}) end end ɹҰ෦ includes ࡁͷέʔε
100. AssociationsBuilder
101. 
     AssociationsBuilder module BulletmarkRepairer class AssociationsBuilder def build(marker) return if marker.skip? if associations[marker.index] associations[marker.index].add(marker) else associations[marker.index] = Associations.new( marker, @application_associations, @loaded_associations ) end end end end ɹBullet ͷܯࠂΛந৅Խͨ͠ 
 ɹΠϯελϯε
102. 
     AssociationsBuilder module BulletmarkRepairer class AssociationsBuilder def build(marker) return if marker.skip? if associations[marker.index] associations[marker.index].add(marker) else associations[marker.index] = Associations.new( marker, @application_associations, @loaded_associations ) end end end end ɹN+1 ൃੜՕॴΛΩʔʹͯ͠ 
 ɹ ɹ
103. 
     AssociationsBuilder module BulletmarkRepairer class AssociationsBuilder def build(marker) return if marker.skip? if associations[marker.index] associations[marker.index].add(marker) else associations[marker.index] = Associations.new( marker, @application_associations, @loaded_associations ) end end end end ɹN+1 ൃੜՕॴΛΩʔʹͯ͠ 
 ɹassociation Λ૊ΈཱͯΔ
104. 
     AssociationsBuilder module BulletmarkRepairer class AssociationsBuilder def build(marker) return if marker.skip? if associations[marker.index] associations[marker.index].add(marker) else associations[marker.index] = Associations.new( marker, @application_associations, @loaded_associations ) end end end end
     2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:actors] Add to your query: .includes([:actors]) 2023-10-23 07:21:04[WARN] user: makicamel GET /plays USE eager loading detected Play => [:theaters] Add to your query: .includes([:theaters]) ɹෳ਺ͷܯࠂΛ 
 ɹͻͱͭʹ·ͱΊ͍ͨ 
 ɹέʔε͕͋Δ
105. AssociationsBuilder •γϯϘϧΛϋογϡʹͨ͠Γ 
 [:actor]ɹˠɹ[{ actor: [:company] }] •ϋογϡͷόϦϡʔΛ഑ྻʹม׵ͯ͠஋Λ௥Ճͨ͠Γ 
 [{ actors: :company }, :staffs] 
 ɹˠɹ[{ actors: [:company, :works] }, :staffs] •഑ྻͷ஋ͷͻͱͭͱ௥Ճ͍ͨ͠஋Λϋογϡʹม׵ͨ͠Γ 
 [{ actors: :works }]ɹˠɹ[{ actors: { works: [:staffs] } }] ͳΜ͔΋͍ͯ͠Δ ɹෳ਺ͷܯࠂΛ 
 ɹͻͱͭʹ·ͱΊ͍ͨ 
 ɹέʔε͕͋Δ
106. LoadedAssociations
107. 
     
     2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' class PlaysController < ApplicationController def index @plays = Play.includes(:actors) end end ɹҰ෦ includes ࡁͷέʔε LoadedAssociations
108. 
     
     2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' class PlaysController < ApplicationController def index @plays = Play.includes(:actors).includes({:actors=>[:company]}) end end ɹҰ෦ includes ࡁͷέʔε LoadedAssociations
109. 
     
     2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' class PlaysController < ApplicationController def index @plays = Play.includes(:actors).includes({:actors=>[:company]}) end end ɹBullet ͷܯࠂ͔Β͸ 
 ɹ@plays ͷϕʔεͷΫϥε͕ 
 ɹԿ͔Θ͔Βͳ͍ LoadedAssociations
110. 
     
     2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' ɹBullet ͷܯࠂ͔Β͸ͲͪΒ͕ 
 ɹਖ਼͍͔͠Θ͔Βͳ͍ LoadedAssociations class PlaysController < ApplicationController def index @plays = Play.includes(:actors).includes({:actors=>[:company]}) end end .includes([:company])
111. 
     LoadedAssociations module BulletmarkRepairer module ActiveRecord module QueryMethod def includes(*args) Thread.current[:bulletmark_repaier_loaded_associations][model.name][:includes].add(args) super(args) end def eager_load(*args) Thread.current[:bulletmark_repaier_loaded_associations][model.name][:eager_load].add(args) super(args) end def preload(*args) Thread.current[:bulletmark_repaier_loaded_associations][model.name][:preload].add(args) super(args) end end end end ɹಡΈࠐΈࡁͷ associations Λ 
 ɹϝϞ͓ͯ͘͠
112. 
     LoadedAssociations ɹassociation Λ૊ΈཱͯΔ࣌ʹ 
 ɹࢀর͢Δ class Associations def initialize(marker, application_associations, loaded_associations) @marker = marker @application_associations = application_associations @loaded_associations = loaded_associations key = @loaded_associations.key(marker.base_class) @associations = { base: key ? { key => marker.associations } : marker.associations } end end
113. 
     
     2023-10-26 14:46:46[WARN] user: makicamel GET /plays USE eager loading detected Actor => [:company] Add to your query: .includes([:company]) Call stack /Users/makicamel/awesome_app/app/views/plays/index.html.erb:3:in `block (2 levels) in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:2:in `block in _app_views_plays_index_html_erb__2119670124553133993_11760' /Users/makicamel/awesome_app/app/views/plays/index.html.erb:1:in `_app_views_plays_index_html_erb__2119670124553133993_11760' ɹactors ͸ includes ࡁͳͷͰ 
 ɹωετ͢Δͷ͕ਖ਼͍͠ 💡 LoadedAssociations class PlaysController < ApplicationController def index @plays = Play.includes(:actors).includes({:actors=>[:company]}) end end .includes([:company])
114. •Ͳ͜Ͱ includes ͢Δ΂͖͔ ✓ •ͳʹΛ includes ͢Δ΂͖͔ ✓ ͋ͱ͸ Parer ʹ͓೚ͤ
115. ☕
116. ͨͿΜΈͳ͞Μ͕ؾʹͳ͍ͬͯΔ͜ͱ
117. includes vs. preload or eager_load
118. includes vs. preload or eager_load
119. ൃߦ͞ΕΔΫΤϦ͕มΘΔ৚݅͸ࣗ໌ͳͷʹ 
 Ͳ͏ͯ͠࢖͍෼͚͍ͨΜ͚ͩͬʁ includes vs. preload or eager_load
120. •preload ͕޷·͍͠έʔε͕ଟ͍ •eager_load ͸ LEFT OUTER JOIN ͳͷͰϝϞϦΛ৯͍΍͍͢ •preload ͷ৔߹ IN ۟ʹೖΔ id ͷ਺͕ଟ͘ʢe.g. ਺ສ݅ʣͳΔͱ 
 ύϑΥʔϚϯε͕ஶ͘͠௿Լ͢Δ͜ͱ͕͋Δ •preload or eager_load Ҏ֎ͷํ๏΋͋Δ preload vs. eager_load ઈରղ͸ͳ͍
121. •includes ͩͱύϥϝʔλ΍ঢ়ଶʹΑΓ preload or eager_load ͕ 
 ࢖͍෼͚ΒΕΔ͜ͱ͕͋Δ •ϦΫΤετʹΑΓൃߦ SQL ͕มΘΔͱ෼ੳͮ͠Β͍ includes vs. preload or eager_load ෼ੳɾӡ༻໘Ͱ includes ΑΓ preload or eager_load ͕޷·͍͠
122. ϝϞϦѹഭ͕৺഑ͳΜͰ͚͢Ͳ... N+1 → LEFT JOIN ͰϝϞϦ͕໰୊ʹͳΔͳΒ 
 ଟ͘ͷ৔߹ N+1 ͷ࣌఺Ͱ 
 ໰୊ʹͳ͍ͬͯΔͱࢥ͍·͢Α includes vs. preload or eager_load @tricknotes
123. N+1 < includes < preload or eager_load (or ͦͷଞ) ͷ࢖͍෼͚ includes vs. preload or eager_load
124. ݱ࣮ੈքͷ 
 N+1 ໰୊ͱͷ޲͖߹͍ํ
125. •๩͍͠
126. •ΘΕΘΕ͸๩͍͠ •΍Γ͍ͨ͜ͱΛ͢΂ͯͰ͖ΔΘ͚Ͱ͸ͳ͍ N+1 ໰୊ͱͷ޲͖߹͍ํ
127. •޲͖߹͑Δ࣌ʹ͸޲͖߹͑Δ •৽͘͠ίʔυΛॻ࣌͘ •طଘͷίʔυΛ֦ு͢Δ࣌ •N+1 ͕໰୊ʹͳ͍ͬͯΔ࣌ N+1 ໰୊ͱͷ޲͖߹͍ํ
128. •޲͖߹͍ʹ͍࣌͘ •ࣗ෼ͷαʔϏεͰݩʑ͋ͬͨ N+1 ໰୊ •௨Γ͕͢Γʹݟ͚ͭͨ N+1 ໰୊ N+1 ໰୊ͱͷ޲͖߹͍ํ
129. •ͨ·ͨ·ݟ͚ͭͨطଘͷ N+1 ໰୊ •SQL ͷมߋ͸ϦεΩʔ •౔஍צ͕ͳ͍ͱεϧʔ͕ͪ͠ •େ͖ͳαʔϏεʹͳΔͱྡͷ౔஍ͷ͜ͱΛ஌Βͳ͔ͬͨΓ͢Δ N+1 ໰୊ͱͷ޲͖߹͍ํ
130. ໨ͷલʹ͝Έ͕མͪͯͨΒ 
 र͏͡Όͳ͍Ͱ͔͢ @a_matsuda
131. ݱঢ়ͷANDPADͷվળ͍ͨ͠ͱ͜ΖΛ ざ ͬ͘ ば ΒΜʹʢANDPAD ࣾ಺։࠵ʣ 2020 ೥ 5 ݄ 22 ೔ @a_matsuda
132. •ͨ·ͨ·ݟ͚ͭͨ N+1 ΛͱΓ͋͑ͣ௚ͯ͠ PR Λ࡞Δਓ •PR ΛϤγ 👈 ͯ͠औΓࠐΉਓ N+1 ୀ࣏൪௕ BulletmarkRepairer ͸ 
 ͜ͷ෦෼ͷ 
 αϙʔτπʔϧ 🩹
133. •ͨ·ͨ·ݟ͚ͭͨ N+1 ΛͱΓ͋͑ͣ௚ͯ͠ PR Λ࡞Δਓ •PR ΛϤγ 👈 ͯ͠औΓࠐΉਓ •ൃߦ͞ΕΔ SQL ͷมԽͷ֬ೝ •࣮σʔλ্໰୊ͳͦ͞͏͔ͷ֬ೝ ͜ͷϓϩηεվળ΋ 
 ͔͚ͨͬͨ͠Ͳ 
 ؒʹ߹Θͳ͔ͬͨ ͜ͷϓϩηε΋ 
 վળ͍ͨ͠ 
 ʢؒʹ߹Θͳ͔ͬͨʣ N+1 ୀ࣏൪௕
134. N+1 ໰୊ͱͷ޲͖߹͍ํ
135. •શ෦ includes (preload or eager_load) ͢Ε͹ղܾ •Ͱ͸ͳ͍ N+1 ໰୊ͷղ๏
136. •AR#present? → AR#exists? / AR#map → AR#pluck N+1 ໰୊ͷղ๏ ద੾ͳϝιουΛ 
 ࢖͏
137. •e.g. Ұ෦ͷ৚݅࣌ͷΈಡΈࠐΜͩϨίʔυ͕ར༻͞ΕΔέʔε 
 → ෆཁͳΒಡΈࠐ·ͳ͍ •e.g. ϙϦϞʔϑΟοΫؔ࿈ͷ 
 ಛఆͷؔ࿈ͰͷΈϨίʔυ͕ར༻͞ΕΔέʔε 
 → ෆཁͳΒಡΈࠐ·ͳ͍ N+1 ໰୊ͷղ๏ ෆཁͳΒ 
 ಡΈࠐ·ͳ͍
138. •ղ๏͸༷ʑ •୯७Ͱୀ۶ͳ΋ͷ •೉ͯ͘͠಄ʹ׼ͯ͠ؤுΔ΋ͷ N+1 ໰୊ͱͷ޲͖߹͍ํ
139. N+1 ໰୊ͱͷ޲͖߹͍ํ Ruby ୀ۶ͳ͜ͱ͸Pythonʹ΍ΒͤΑ͏ɹϊϯϓϩάϥϚʔʹ΋Ͱ͖ΔࣗಈԽॲཧϓϩάϥϛϯά
 Al Sweigart ஶ ૬઒ Ѫࡾ ༁
140. •୯७Ͱୀ۶ͳ͜ͱ͸ Ruby ʹ΍ΒͤΑ͏ •೉ͯ͘͠໘ന͍໰୊͸ਓ͕ؒղ͜͏ N+1 ໰୊ͱͷ޲͖߹͍ํ
141. ໘ന͍͜ͱΛ΍͍͖ͬͯ·͠ΐ͏
142. ͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ Special Thanks @tricknotes @ydah @l15n @ken3ypa @pupupopo88