<% end %> @posts post.author SELECT * FROM authors WHERE id = 13; SELECT * FROM authors WHERE id = 15; SELECT * FROM authors WHERE id = 21; SELECT * FROM authors WHERE id = 33; SELECT * FROM authors WHERE id = 37; SELECT * FROM posts LIMIT 10;
class PostsController < ApplicationController def index @posts = Post.limit(10) end end @posts = Post.limit(10).includes(:author) SELECT * FROM posts LIMIT 10; SELECT * FROM authors WHERE id IN (13, 15, 21, 33, 37, 42, 46, 47, 53, 55);
LessonCompletion Load (1.6ms) SELECT "lesson_completions".* FROM ... => EXPLAIN for: SELECT "lesson_completions".* FROM "lesson_completions" ... ----------------------------------------------------------------------- Index Scan using index_lesson_completions_on_student_id on ... Filter: (student_id = 3074) (2 rows) 1.6ms Index Scan using index_lesson_completions_on_student_id
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