Rails N+1 Safe

.includes(ごちゃごちゃ) の代わりに .n1_safe をつけるだけでN+1クエリを回避してくれる奴

gemfile

gem 'n1_safe', github: 'tompng/n1_safe'

controller

includesとかはせずにとりあえずn1_safeを付けておく

def index
  @posts = Post.where(foo: :bar).n1_safe
end
def show
  @post = Post.find(params[:id]).n1_safe
  #Post load (X.Xms) SELECT "posts".* FROM "posts" WHERE "posts"."id" = 1 LIMIT 1
end

view

なにも考えずにeachとかまわしまくると、必要になった時にまとめてN+1を回避しつつloadされる感じ

<!-- index.html.erb -->
<% @posts.each do |post| %>
  <h1><%= post.title %> | <%= post.user.name %></h1>
  <p><%= post.body %></p>
  <% post.comments.each do |comment| %>
    <%= comment.user.name %>
    <%= comment.text %>
    <%= comment.stars.count %>
  <% end %>
<% end %>
<!--
#Post load (X.Xms) SELECT "posts".* FROM "posts" WHERE "posts"."foo" = "bar"
#User load (X.Xms) SELECT "users".* FROM "users" WHERE "users"."id" IN (1,3)
#Comment load (X.Xms) SELECT "comments".* FROM "comments" WHERE "comments"."post_id" IN (1,2)
#User load (X.Xms) SELECT "users".* FROM "users" WHERE "users"."id" IN (3,4,5)
# (X.Xms) SELECT COUNT(*) AS count_all, "comment"."id" as comment_id FROM "comments" INNER JOIN "stars" ON "stars"."comment_id" = "comment"."id" WHERE "comment"."id" IN (1,2,3,4,7,8) GROUP BY "comment"."id"
-->

<!-- show.html.erb -->
<%= post.title %><%= post.body %>
<% post.comments.each do |comment| %>
  <%= comment.user.name %>
<% end %>
<!--
#Comments load (X.Xms) SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1
#User load (X.Xms) SELECT "users".* FROM "users" WHERE "users"."id" IN (3,4)
-->