Slide 43
Slide 43 text
> Lesson.where(id: 2).present?
Lesson Load (1.5ms) SELECT "lessons".* FROM "lessons" WHERE
"lessons"."id" = $1 [["id", 2]]
=> false
vs.
> Lesson.where(id: 2).any?
(0.4ms) SELECT COUNT(*) FROM "lessons" WHERE "lessons"."id" = $1
[["id", 2]]
=> false
vs.
> Lesson.where(id: 2).exists?
Lesson Exists (0.4ms) SELECT 1 AS one FROM "lessons" WHERE
"lessons"."id" = $1 LIMIT $2 [["id", 2], ["LIMIT", 1]]
=> false