Querying ActiveStorage Attachments

The problem

You want to find all the ActiveRecord models that either do / do not have a record attached to them.

The solution

Let's say you have a Post class which has one image attached like so:

class Post < ApplicationRecord
  has_one_attached :image
end

To query for all Posts that do not have an image attached the syntax would look like this:

Post.left_joins(:image_attachment).where(active_storage_attachments: { id: nil })

This will return all posts that do not have an image. If you want to find all posts that have an image attached, you would use a #not clause in there like so:

Post.left_joins(:image_attachment).where.not(active_storage_attachments: { id: nil })

has_many_attached

This can even be extended to has_many_attached by using the plural form of :image_attachment like so:

class Post < ApplicationRecord
  has_many_attached :images
end

# Query for all without attachments
Post.left_joins(:image_attachments).where(active_storage_attachments: { id: nil })

# Query for all with attachments
Post.left_joins(:image_attachments).where.not(active_storage_attachments: { id: nil })

Final Syntax

The syntax for attachments is fairly straightforward like so:

ModelName.left_joins(:<attachment_name>_attachment[s]).where(active_storage_attachments: { <column>: <value> })

And thats it! Good luck and enjoy your new found query power!