{"id":12742,"date":"2021-01-09T09:56:50","date_gmt":"2021-01-09T00:56:50","guid":{"rendered":"http:\/\/www.code-magagine.com\/?p=12742"},"modified":"2023-05-27T22:39:51","modified_gmt":"2023-05-27T13:39:51","slug":"%e3%80%90ruby-on-rails%e3%80%91%e3%80%8cbullet%e3%80%8d%e3%81%ab%e3%81%a4%e3%81%84%e3%81%a6","status":"publish","type":"post","link":"http:\/\/www.code-magagine.com\/?p=12742","title":{"rendered":"\u3010Ruby on Rails\u3011\u300cbullet\u300d\u3001\u300cN+1\u554f\u984c\u300d\u306b\u3064\u3044\u3066"},"content":{"rendered":"

\u6e96\u5099<\/h2>\n

\u307e\u305a\u306f\u3001\u30e2\u30c7\u30eb\u3092\u4f5c\u6210\u3057\u307e\u3059\u3002<\/p>\n

rails g model user name:string\r\nrails g model post name:string<\/pre>\n
\u30de\u30a4\u30b0\u30ec\u30fc\u30b7\u30e7\u30f3\u30d5\u30a1\u30a4\u30eb\u3092\u305d\u308c\u305e\u308c\u4f5c\u6210\u3057\u307e\u3059\u3002<\/p>\n
user<\/h3>\n
class CreateUsers < ActiveRecord::Migration[6.0]\r\n  def change\r\n    create_table :users do |t|\r\n      t.string :name\r\n\r\n      t.timestamps\r\n    end\r\n  end\r\nend\r\n<\/pre>\n
post<\/h3>\n
class CreatePosts < ActiveRecord::Migration[6.0]\r\n  def change\r\n    create_table :posts do |t|\r\n      t.string :name\r\n      t.references :user\r\n\r\n      t.timestamps\r\n    end\r\n  end\r\nend<\/pre>\n
model\u30d5\u30a1\u30a4\u30eb\u3082\u305d\u308c\u305e\u308c\u8a2d\u5b9a\u3057\u307e\u3059\u3002<\/p>\n
user<\/h3>\n
class User < ApplicationRecord\r\n  has_many :posts\r\nend\r\n<\/pre>\n
post<\/h3>\n
class Post < ApplicationRecord\r\n  belongs_to :user\r\nend<\/pre>\n
\u30c7\u30fc\u30bf\u6295\u5165<\/h3>\n
\u300cuser\uff1apost = 1:\u591a\u300d\u306b\u306a\u308b\u3088\u3046\u306b\u30c7\u30fc\u30bf\u3092\u4f5c\u6210\u3057\u307e\u3059\u3002(rails c\u3067Rails\u30b3\u30f3\u30bd\u30fc\u30eb\u4e0a\u3067\u5b9f\u884c\u3059\u308b\u3068\u826f\u3044\u3067\u3057\u3087\u3046\u3002)\u3001\u305f\u3060\u3001user\u306f1\u3067\u3059\u304c\u3001N+1\u554f\u984c\u3092\u518d\u73fe\u3059\u308b\u305f\u3081\u306b\u8907\u6570\u4eba\u4f5c\u6210\u3057\u307e\u3059\u3002<\/p>\n
user(1)<\/h4>\n
user1 = User.create!(name:\"\u592a\u90ce\")\r\nuser2 = User.create!(name:\"\u82b1\u5b50\")\r\nuser3 = User.create!(name:\"\u6b21\u90ce\")<\/pre>\n
post(\u591a)<\/h4>\n
user1.posts.create!(name:\"\u6295\u7a3f1\")\r\nuser1.posts.create!(name:\"\u6295\u7a3f2\")\r\nuser2.posts.create!(name:\"\u6295\u7a3f1\")\r\nuser2.posts.create!(name:\"\u6295\u7a3f2\")\r\nuser2.posts.create!(name:\"\u6295\u7a3f3\")\r\nuser3.posts.create!(name:\"\u6295\u7a3f1\")\r\nuser3.posts.create!(name:\"\u6295\u7a3f2\")\r\nuser3.posts.create!(name:\"\u6295\u7a3f3\")<\/pre>\n
\u30b3\u30f3\u30c8\u30ed\u30fc\u30e9\u306e\u4f5c\u6210<\/h3>\n
rails g controller users index<\/pre>\n
\u30b3\u30f3\u30c8\u30ed\u30fc\u30e9\u5074<\/h4>\n
class UsersController < ApplicationController\r\n  def index\r\n    @users = User.all\r\n  end\r\nend<\/pre>\n
\u30d3\u30e5\u30fc\u5074<\/h4>\n
<% @users.each do |user| %>\r\n  <%= user.name %> |\r\n  <% user.posts.each do |post| %>\r\n    <%= post.name %>\r\n  <% end %>\r\n  <br>\r\n<% end %><\/pre>\n
url<\/h4>\n
http:\/\/localhost:3000\/users<\/pre>\n
\u4e0a\u8a18URL\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3068\u4e0b\u8a18\u306e\u3088\u3046\u306a\u611f\u3058\u3067select\u6587\u304c\u5927\u91cf\u306b\u767a\u884c\u3055\u308c\u308bN+1\u554f\u984c<\/strong><\/span>\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n
\"\"<\/p>\n
bullet\u306e\u5c0e\u5165<\/h2>\n
bullet\u306f\u958b\u767a\u74b0\u5883\u3067\u3057\u304b\u57fa\u672c\u4f7f\u308f\u306a\u3044\u306e\u3067development\u30b0\u30eb\u30fc\u30d7\u914d\u4e0b\u306b\u8a2d\u5b9a\u3057\u307e\u3059\u3002<\/p>\n
group :development do\r\n  gem 'bullet'\r\nend<\/pre>\n
bundle\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3057\u307e\u3059\u3002<\/p>\n
bundle install<\/pre>\n
\u4ee5\u4e0b\u306e\u5834\u6240\u306e\u8a2d\u5b9a\u30d5\u30a1\u30a4\u30eb\u306bbullet\u3067\u691c\u77e5\u3067\u304d\u308b\u3088\u3046\u306b\u8a2d\u5b9a\u3057\u307e\u3059\u3002<\/p>\n
config\/environments\/development.rb<\/pre>\n
\u8a2d\u5b9a\u5185\u5bb9<\/h3>\n
config.after_initialize do\r\n  Bullet.enable = true\r\n  Bullet.alert = true\r\n  Bullet.bullet_logger = true\r\n  Bullet.console = true\r\n  Bullet.rails_logger = true\r\nend\r\n<\/pre>\n
Rails\u30b5\u30fc\u30d0\u30fc\u3092\u518d\u8d77\u52d5\u3057\u307e\u3059\u3002<\/p>\n
rails s<\/pre>\n
\u307e\u305f\u3001\u4e0a\u8a18URL\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3068\u4e0b\u8a18\u306e\u30dd\u30c3\u30d7\u30a2\u30c3\u30d7\u8868\u793a\u304c\u306a\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n
\"\"<\/p>\n
\u30dd\u30c3\u30d7\u30a2\u30c3\u30d7\u306e\u6307\u793a\u901a\u308a\u30b3\u30f3\u30c8\u30ed\u30fc\u30e9\u306e\u30af\u30a8\u30ea\u306b\u300cincludes(:posts)\u300d\u3092\u8ffd\u52a0\u3057\u307e\u3059\u3002<\/p>\n
@users = User.all.includes(:posts)<\/pre>\n
\u518d\u3073\u30da\u30fc\u30b8\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3068\u4eca\u5ea6\u306fSQL\u304c\u4e0b\u8a18\u306e\u3088\u3046\u306b\u306a\u308a\u30dd\u30c3\u30d7\u30a2\u30c3\u30d7\u304c\u51fa\u306a\u304f\u306a\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n
  User Load (0.3ms)  SELECT \"users\".* FROM \"users\"\r\n  \u21b3 app\/views\/users\/index.html.erb:1\r\n  Post Load (0.2ms)  SELECT \"posts\".* FROM \"posts\" WHERE \"posts\".\"user_id\" IN (?, ?, ?)  [[\"user_id\", 1], [\"user_id\", 2], [\"user_id\", 3]]<\/pre>\n
\u4f59\u5206\u306a\u5834\u5408\u3082\u3042\u308b\u3002<\/h2>\n
\u4f59\u5206\u306bincludes\u7b49\u306eN+1\u5bfe\u7b56\u3092\u3057\u3066\u3057\u307e\u3063\u3066\u3044\u308b\u5834\u5408\u306f\u9006\u306b\u4e0b\u8a18\u306e\u3088\u3046\u306a\u30e1\u30c3\u30bb\u30fc\u30b8\u304c\u51fa\u307e\u3059\u3002<\/p>\n
AVOID eager loading detected\r\nRemove to your query: .includes([:\u30e2\u30c7\u30eb\u540d])<\/pre>\n
\u305d\u306e\u5834\u5408\u306fincludes\u7b49\u3092\u5916\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n
N+1\u554f\u984c\u3068\u306f\uff1f<\/h2>\n
Rails\u3067\u30eb\u30fc\u30d7\u51e6\u7406\u306e\u90fd\u5ea6SQL\u3092\u767a\u884c\u3057\u3066\u3057\u307e\u3044\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u304c\u4f4e\u4e0b\u3059\u308b\u554f\u984c\u306e\u3053\u3068\u3067\u3059\u3002<\/p>\n
\u5177\u4f53\u7684\u306b\u306f\u3069\u3093\u306a\u52d5\u4f5c\u304b\uff1f<\/h2>\n
1:\u591a\u306e\u30ea\u30ec\u30fc\u30b7\u30e7\u30f3\u306e\u30c6\u30fc\u30d6\u30eb\u540c\u58eb\u30671\u306b\u7d10\u3065\u3044\u3066\u3044\u308b\u591a\u306e\u60c5\u5831\u3092\u53d6\u5f97\u3057\u3088\u3046\u3068\u3057\u305f\u969b\u306b\u3001\u6700\u521d\u306b\u4e00\u62ec\u30671\u306e\u65b9\u306e\u30c6\u30fc\u30d6\u30eb\u306e\u30c7\u30fc\u30bf\u3092SQL\u3067\u53d6\u5f97\u3057\u305f\u5f8c\u306b\u3001\u4ed6\u306e\u591a\u306e\u65b9\u306e\u95a2\u9023\u30c7\u30fc\u30bf\u30921\u4ef61\u4ef6\u305a\u3064\u5408\u8a08N\u4ef6\u306b\u306a\u308b\u307e\u3067SQL\u3092\u767a\u884c\u3057\u7d9a\u3051\u307e\u3059\u3002<\/strong><\/span>\u6570\u4ef6\u7a0b\u5ea6\u3067\u3042\u308c\u3070\u554f\u984c\u306a\u3044\u306e\u3067\u3059\u304c\u30c7\u30fc\u30bf\u91cf\u304c\u5897\u3048\u308b\u3068\u591a\u5927\u306a\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u640d\u5931\u306b\u7e4b\u304c\u308a\u304b\u306d\u307e\u305b\u3093\u3002<\/p>\n
\u5177\u4f53\u4f8b<\/h3>\n
\u5177\u4f53\u7684\u306b\u306fjoins\u3092\u5229\u7528\u3057\u3066\u3044\u3066\u7d50\u5408\u3057\u305f\u30c6\u30fc\u30d6\u30eb\u3092\u30eb\u30fc\u30d7\u3057\u3066\u95a2\u9023\u5148\u306e\u30c6\u30fc\u30d6\u30eb\u306e\u30c7\u30fc\u30bf\u3092\u53c2\u7167\u3057\u3088\u3046\u3068\u3057\u305f\u5834\u5408\u306b\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n
projects = Project.joins(:category_projects)\r\n  Project Load (7.5ms)  SELECT \"projects\".* FROM \"projects\" INNER JOIN \"category_projects\" ON \"category_projects\".\"project_id\" = \"projects\".\"id\" LIMIT ?  [[\"LIMIT\", 11]]\r\n=> #<ActiveRecord::Relation [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]>\r\n\r\nirb(main):011:0> projects.each do |project| p project.category_projects end\r\n  CategoryProject Load (0.8ms)  SELECT \"category_projects\".* FROM \"category_projects\" WHERE \"category_projects\".\"project_id\" = ? LIMIT ?  [[\"project_id\", 1], [\"LIMIT\", 11]]\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 1, category_id: 1, project_id: 1, created_at: \"2020-12-19 09:56:20\", updated_at: \"2020-12-19 09:56:20\">]>\r\n  CategoryProject Load (0.5ms)  SELECT \"category_projects\".* FROM \"category_projects\" WHERE \"category_projects\".\"project_id\" = ? LIMIT ?  [[\"project_id\", 2], [\"LIMIT\", 11]]\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 2, category_id: 1, project_id: 2, created_at: \"2020-12-19 09:56:28\", updated_at: \"2020-12-19 09:56:28\">]>\r\n=> [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]<\/pre>\n
\u4e0a\u8a18\u4f8b\u3067\u306f\u300cProject\uff1aCategory_project\u300d\uff1d\u300c1:\u591a\u300d\u306b\u306a\u3063\u3066\u3044\u308b\u5834\u5408\u3067\u95a2\u9023\u5148\u306e\u30c6\u30fc\u30d6\u30eb\u3092\u547c\u3076\u305f\u3073\u306bSELECT\u6587\u304c\u547c\u3070\u308c\u3066\u3044\u308b\u3053\u3068\u304c\u308f\u304b\u308a\u307e\u3059\u3002\u3053\u308c\u306fjoins\u306e\u7279\u6027\u3068\u3057\u3066\u30e1\u30e2\u30ea\u4e0a\u306b\u95a2\u9023\u5148\u30c6\u30fc\u30d6\u30eb\u60c5\u5831\uff08CategoryProject\uff09\u307e\u3067\u30ad\u30e3\u30c3\u30b7\u30e5\u3057\u306a\u3044\u305f\u3081\u3067\u3059\u3002<\/strong><\/span><\/p>\n
N+1\u554f\u984c\u3078\u306e\u5bfe\u7b56<\/h2>\n
\u4e0b\u8a18\u306eActiveRecord\u306e\u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u3046\u3053\u3068\u306b\u3088\u308a\u6bd4\u8f03\u7684\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u8ca0\u8377\u3092\u8efd\u6e1b\u3067\u304d\u307e\u3059\u3002\u3069\u3061\u3089\u3082\u51e6\u7406\u306e\u524d\u306bassociation\u3092\u30ad\u30e3\u30c3\u30b7\u30e5\u3059\u308b\u3053\u3068\u306b\u3088\u308aN\u56de\u306eSQL\u5b9f\u884c\u30921\u56de\u306b\u307e\u3068\u3081\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/strong><\/span><\/p>\n
    \n
  • preload\u30e1\u30bd\u30c3\u30c9<\/li>\n
  • eager_load\u30e1\u30bd\u30c3\u30c9<\/li>\n<\/ul>\n
    preload\u30e1\u30bd\u30c3\u30c9<\/h3>\n
    IN\u53e5\u3092\u4f7f\u3063\u3066SQL\u3092\u4e00\u3064\u306b\u307e\u3068\u3081\u307e\u3059\u3002\u3042\u307e\u308aJOIN\u3057\u305f\u304f\u306a\u3044\u3067\u304b\u3044\u30c6\u30fc\u30d6\u30eb\u540c\u58eb\u306e\u7d50\u5408\u306e\u969b\u306f\u3053\u3061\u3089\u3092\u4f7f\u3046\u3068\u826f\u3044\u3067\u3057\u3087\u3046\u3002<\/p>\n
    irb(main):019:0> projects = Project.preload(:category_projects)\r\n  Project Load (5.7ms)  SELECT \"projects\".* FROM \"projects\" LIMIT ?  [[\"LIMIT\", 11]]\r\n  CategoryProject Load (0.6ms)  SELECT \"category_projects\".* FROM \"category_projects\" WHERE \"category_projects\".\"project_id\" IN (?, ?)  [[\"project_id\", 1], [\"project_id\", 2]]\r\n=> #<ActiveRecord::Relation [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]>\r\n\r\nirb(main):020:0> projects.each do |project| p project.category_projects end\r\n  Project Load (0.8ms)  SELECT \"projects\".* FROM \"projects\"\r\n  CategoryProject Load (0.4ms)  SELECT \"category_projects\".* FROM \"category_projects\" WHERE \"category_projects\".\"project_id\" IN (?, ?)  [[\"project_id\", 1], [\"project_id\", 2]]\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 1, category_id: 1, project_id: 1, created_at: \"2020-12-19 09:56:20\", updated_at: \"2020-12-19 09:56:20\">]>\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 2, category_id: 1, project_id: 2, created_at: \"2020-12-19 09:56:28\", updated_at: \"2020-12-19 09:56:28\">]>\r\n=> [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]<\/pre>\n
    eager_load\u306e\u4f7f\u3044\u5206\u3051\u3068\u3057\u3066\u306f\u3001\u300c1\uff1a\u591a\u300d\u3067\u30c7\u30fc\u30bf\u91cf\u304c\u591a\u3044\u30c6\u30fc\u30d6\u30eb\u306e\u7d50\u5408\u306e\u969b\u306b\u4f7f\u7528\u3059\u308b<\/strong><\/span>\u3068\u826f\u3044\u3067\u3057\u3087\u3046\u3002<\/p>\n
    where\u304c\u4f7f\u3048\u306a\u3044\u3002<\/h4>\n
    \u76f8\u624b\u5148\u306e\u30c6\u30fc\u30d6\u30eb\u306e\u7d5e\u308a\u8fbc\u307f\u3092\u3057\u3088\u3046\u3068\u3057\u3066\u3001where\u3092\u4f7f\u3046\u3068\u30a8\u30e9\u30fc\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n
    irb(main):030:0> projects = Project.preload(:category_projects).where(category_projects: { project_id:1} )\r\n  Project Load (3.6ms)  SELECT \"projects\".* FROM \"projects\" WHERE \"category_projects\".\"project_id\" = ? LIMIT ?  [[\"project_id\", 1], [\"LIMIT\", 11]]\r\nTraceback (most recent call last):\r\nActiveRecord::StatementInvalid (SQLite3::SQLException: no such column: category_projects.project_id)\r\n<\/pre>\n
    includes\u30e1\u30bd\u30c3\u30c9<\/h3>\n
    \n
    IN\u53e5\u3092\u4f7f\u3063\u3066SQL\u3092\u4e00\u3064\u306b\u307e\u3068\u3081\u307e\u3059\u3002\u72b6\u6cc1\u306b\u5fdc\u3058\u3066\u3001preload\u304beager_load\u304c\u4f7f\u3044\u5206\u3051\u3089\u308c\u307e\u3059\u3002\u305d\u308c\u307b\u3069\u5b9f\u52d9\u3067\u5f71\u97ff\u304c\u3042\u308b\u308f\u3051\u3067\u306f\u3042\u308a\u307e\u305b\u3093\u304c\u3001\u7406\u89e3\u3092\u6df1\u3081\u3089\u308c\u305f\u65b9\u3067\u3042\u308c\u3070\u610f\u56f3\u7684\u306bpreload\u304beager_load\u304b\u3092\u9078\u629e\u3059\u308b\u3088\u3046\u306b\u3057\u307e\u3057\u3087\u3046\u3002<\/div>\n
    \n
    irb(main):023:0> projects = Project.includes(:category_projects)\r\n  Project Load (1.6ms)  SELECT \"projects\".* FROM \"projects\" LIMIT ?  [[\"LIMIT\", 11]]\r\n  CategoryProject Load (2.4ms)  SELECT \"category_projects\".* FROM \"category_projects\" WHERE \"category_projects\".\"project_id\" IN (?, ?)  [[\"project_id\", 1], [\"project_id\", 2]]\r\n=> #<ActiveRecord::Relation [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]>\r\n\r\nirb(main):024:0> projects.each do |project| p project.category_projects end\r\n  Project Load (0.4ms)  SELECT \"projects\".* FROM \"projects\"\r\n  CategoryProject Load (4.4ms)  SELECT \"category_projects\".* FROM \"category_projects\" WHERE \"category_projects\".\"project_id\" IN (?, ?)  [[\"project_id\", 1], [\"project_id\", 2]]\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 1, category_id: 1, project_id: 1, created_at: \"2020-12-19 09:56:20\", updated_at: \"2020-12-19 09:56:20\">]>\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 2, category_id: 1, project_id: 2, created_at: \"2020-12-19 09:56:28\", updated_at: \"2020-12-19 09:56:28\">]>\r\n=> [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]<\/pre>\n
    eager_load\u30e1\u30bd\u30c3\u30c9<\/h3>\n<\/div>\n<\/div>\n
    LEFT OUTER JOIN\u3092\u4f7f\u3063\u3066SQL\u3092\u4e00\u3064\u306b\u307e\u3068\u3081\u307e\u3059\u3002<\/p>\n
    irb(main):015:0> projects = Project.eager_load(:category_projects)\r\n  SQL (0.5ms)  SELECT DISTINCT \"projects\".\"id\" FROM \"projects\" LEFT OUTER JOIN \"category_projects\" ON \"category_projects\".\"project_id\" = \"projects\".\"id\" LIMIT ?  [[\"LIMIT\", 11]]\r\n  SQL (0.7ms)  SELECT \"projects\".\"id\" AS t0_r0, \"projects\".\"title\" AS t0_r1, \"projects\".\"created_at\" AS t0_r2, \"projects\".\"updated_at\" AS t0_r3, \"category_projects\".\"id\" AS t1_r0, \"category_projects\".\"category_id\" AS t1_r1, \"category_projects\".\"project_id\" AS t1_r2, \"category_projects\".\"created_at\" AS t1_r3, \"category_projects\".\"updated_at\" AS t1_r4 FROM \"projects\" LEFT OUTER JOIN \"category_projects\" ON \"category_projects\".\"project_id\" = \"projects\".\"id\" WHERE \"projects\".\"id\" IN (?, ?)  [[\"id\", 1], [\"id\", 2]]\r\n\u2191\u95a2\u9023\u5148\u304c\u300c\u591a\u300d\u306b\u306a\u3063\u3066\u3044\u308b\u3068\u4e0a\u306eSQL\u3067DISTINCT\u304c\u767a\u751f\u3057\u3066\u3057\u307e\u3044\u30b3\u30b9\u30c8\u304c\u5897\u3048\u308b\u3002\r\n\r\nirb(main):016:0> projects.each do |project| p project.category_projects end\r\n  SQL (0.8ms)  SELECT \"projects\".\"id\" AS t0_r0, \"projects\".\"title\" AS t0_r1, \"projects\".\"created_at\" AS t0_r2, \"projects\".\"updated_at\" AS t0_r3, \"category_projects\".\"id\" AS t1_r0, \"category_projects\".\"category_id\" AS t1_r1, \"category_projects\".\"project_id\" AS t1_r2, \"category_projects\".\"created_at\" AS t1_r3, \"category_projects\".\"updated_at\" AS t1_r4 FROM \"projects\" LEFT OUTER JOIN \"category_projects\" ON \"category_projects\".\"project_id\" = \"projects\".\"id\"\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 1, category_id: 1, project_id: 1, created_at: \"2020-12-19 09:56:20\", updated_at: \"2020-12-19 09:56:20\">]>\r\n#<ActiveRecord::Associations::CollectionProxy [#<CategoryProject id: 2, category_id: 1, project_id: 2, created_at: \"2020-12-19 09:56:28\", updated_at: \"2020-12-19 09:56:28\">]>\r\n=> [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">, #<Project id: 2, title: \"project2\", created_at: \"2020-12-19 09:54:40\", updated_at: \"2020-12-19 09:54:40\">]<\/pre>\n
    joins\u3068\u540c\u3058\u3088\u3046\u306b\u8a18\u8ff0\u3057\u3066\u3044\u307e\u3059\u304c\u3001\u30eb\u30fc\u30d7\u3092\u56de\u3059\u969b\u306eSQL\u306e\u5b9f\u884c\u304c1\u56de\u3067\u6e08\u3093\u3067\u3044\u308b\u306e\u3067SQL\u767a\u884c\u56de\u6570\u306f\u6700\u5c0f\u306b\u6291\u3048\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u305f\u3060\u3001\u76f8\u624b\u304c\u95a2\u9023\u5148\u30c6\u30fc\u30d6\u30eb\u304cN\u306e\u5834\u5408\u306f\u6700\u521d\u306b\u7d50\u5408\u3059\u308b\u969b\u306b\u3001DISTINCT\u304c\u767a\u751f\u3059\u308b\u306e\u3067\u30c7\u30fc\u30bf\u91cf\u304c\u5c11\u306a\u304f\u3001\u300c\uff11\uff1a\uff11\u300d\u306e\u95a2\u9023\u306e\u5834\u5408\u306e\u307f\u4f7f\u7528\u3059\u308b\u3068\u826f\u3044<\/strong><\/span>\u3067\u3057\u3087\u3046\u3002<\/p>\n
    where\u3082\u4f7f\u3048\u308b\u3002<\/h4>\n
    eager_load\u306a\u3089\u76f8\u624b\u5148\u306e\u30c6\u30fc\u30d6\u30eb\u3067\u7d5e\u308a\u8fbc\u3093\u3060\u7d50\u679c\u3092\u8fd4\u305b\u307e\u3059\u3002<\/p>\n
    irb(main):029:0> projects = Project.eager_load(:category_projects).where(category_projects: { project_id:1} )\r\n  SQL (1.7ms)  SELECT DISTINCT \"projects\".\"id\" FROM \"projects\" LEFT OUTER JOIN \"category_projects\" ON \"category_projects\".\"project_id\" = \"projects\".\"id\" WHERE \"category_projects\".\"project_id\" = ? LIMIT ?  [[\"project_id\", 1], [\"LIMIT\", 11]]\r\n  SQL (174.9ms)  SELECT \"projects\".\"id\" AS t0_r0, \"projects\".\"title\" AS t0_r1, \"projects\".\"created_at\" AS t0_r2, \"projects\".\"updated_at\" AS t0_r3, \"category_projects\".\"id\" AS t1_r0, \"category_projects\".\"category_id\" AS t1_r1, \"category_projects\".\"project_id\" AS t1_r2, \"category_projects\".\"created_at\" AS t1_r3, \"category_projects\".\"updated_at\" AS t1_r4 FROM \"projects\" LEFT OUTER JOIN \"category_projects\" ON \"category_projects\".\"project_id\" = \"projects\".\"id\" WHERE \"category_projects\".\"project_id\" = ? AND \"projects\".\"id\" = ?  [[\"project_id\", 1], [\"id\", 1]]\r\n=> #<ActiveRecord::Relation [#<Project id: 1, title: \"project1\", created_at: \"2020-12-19 09:54:11\", updated_at: \"2020-12-19 09:54:11\">]><\/pre>\n
    includes\u30e1\u30bd\u30c3\u30c9<\/h2>\n
    \u4f8b\u3048\u3070\u3001User\u30c6\u30fc\u30d6\u30eb\u306b1\uff1a\u591a\u306e\u30ea\u30ec\u30fc\u30b7\u30e7\u30f3\u304c\u3042\u308bpc\u30c6\u30fc\u30d6\u30eb\u304c\u3042\u308b\u5834\u5408\u306b\u4e0b\u8a18\u306e\u3088\u3046\u306b\u8a18\u8ff0\u3059\u308b\u5834\u5408<\/p>\n
    User.pc<\/pre>\n
    \u4e0a\u8a18\u306e\u3088\u3046\u306b\u8a18\u8ff0\u3059\u308b\u3068User\u3054\u3068\u306bslect\u6587\u3092\u767a\u884c\u3057\u30661\u3064\u305a\u3064pc\u3092\u53d6\u5f97\u3059\u308b\u52d5\u4f5c\u306b\u306a\u3063\u3066\u3057\u307e\u3044\u307e\u3059\u3002<\/p>\n
    User.includes(:pc)<\/pre>\n
    includes\u3092\u4f7f\u3048\u3070IN\u53e5\u3092\u4f7f\u3063\u3066\u30e6\u30fc\u30b6\u30fc\u306b\u7d10\u3065\u304fpc\u3092\u4e00\u62ec\u3057\u3066\u53d6\u5f97\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"\u6e96\u5099 \u307e\u305a\u306f\u3001\u30e2\u30c7\u30eb\u3092\u4f5c\u6210\u3057\u307e\u3059\u3002 rails g model user name:string rails g model post name:string \u30de\u30a4\u30b0\u30ec\u30fc\u30b7\u30e7\u30f3\u30d5\u30a1\u30a4\u30eb\u3092\u305d\u308c\u305e\u308c\u4f5c\u6210\u3057\u307e\u3059\u3002 user c […]","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[36],"tags":[],"_links":{"self":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/12742"}],"collection":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=12742"}],"version-history":[{"count":11,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/12742\/revisions"}],"predecessor-version":[{"id":20490,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/12742\/revisions\/20490"}],"wp:attachment":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12742"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12742"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12742"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}