Attachments associate records with blobs. Usually that's a one record-many blobs relationship, but it is possible to associate many different records with the same blob. A foreign-key constraint on the attachments table prevents blobs from being purged if they’re still attached to any records.

Methods
P
Instance Public methods
purge()

Synchronously deletes the attachment and purges the blob.

Source: show | on GitHub 

# File activestorage/app/models/active_storage/attachment.rb, line 20
def purge
  delete
  blob&.purge
end
purge_later()

Deletes the attachment and enqueues a background job to purge the blob.

Source: show | on GitHub 

# File activestorage/app/models/active_storage/attachment.rb, line 26
def purge_later
  delete
  blob&.purge_later
end