How do you solve N+1 for ActiveStorage URLs?

Question

How do you preload all the records with their URLs?

This is what I am doing in my jbuilder to get the URLs:

# views/users/index.json.jbuilder
...
json.avatar_url user.avatar.attached? && rails_blob_url(user.avatar)
...


Comment
    has_one :user

User
    has_one_attached :avatar

How would you preload all the users and their avatars?

Comments.includes(users: :avatar)

yields the following error:

ActiveRecord::AssociationNotFoundError (Association named 'avatar' was not found on User; perhaps you misspelled it?)

The same error pops up when executing:

User.includes(:avatar)

You do this for a list of users ? Can you also attach location where you populate this list of users ? — Nermin, Aug 10 '18 at 11:43
What is `user.avatar` and how does it relate to `User`? From your error it seems like it's not an association. Is it an attribute? — 3limin4t0r, Aug 10 '18 at 12:38

score 32 · Accepted Answer · edited Oct 27 '20 at 18:44

32

For a singular attachment named :avatar, Active Storage adds a with_attached_avatar scope that preloads the relevant associations:

@users.with_attached_avatar.each do |user|
  # ...
end

See the API documentation for has_one_attached.

edited Oct 27 '20 at 18:44

Felix

4,510
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answered Aug 10 '18 at 13:07

George Claghorn

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What if I am pulling all comments and trying to preload users and their avatars? – Strawberry Aug 10 '18 at 13:28
11

Ah I found it! ```includes(users: :avatar_attachment)```. Thanks for the help! – Strawberry Aug 10 '18 at 13:33
11

@Strawberry, close. You’ll want to use `includes(users: { avatar_attachment: :blob })` to preload the blobs as well. – George Claghorn Aug 11 '18 at 02:51
Actually :avatar_attachment worked for me and reduced my response time significantly. – Strawberry Aug 11 '18 at 06:23
What to do when Multiple Attachments are Present, I really like the `with_attached_variablename` command – Faizaan Khan Aug 17 '18 at 07:30
3

@FaizaanKhan, an equivalent scope is added for plural attachments: for example, `@users.with_attached_highlights`. – George Claghorn Aug 17 '18 at 15:38
2

Rails 6 doc @ https://api.rubyonrails.org/classes/ActiveStorage/Attached/Model.html#method-i-has_one_attached – Pascal Nov 23 '19 at 18:46

How do you solve N+1 for ActiveStorage URLs?

1 Answers1