FIX: Skip callbacks when migrating.

db/migrate/20161202034856_add_uploads_to_categories.rb

@@ -6,12 +6,12 @@ class AddUploadsToCategories < ActiveRecord::Migration
     transaction do
       Category.find_each do |category|
         logo_upload = Upload.find_by(url: category.logo_url)
-        category.uploaded_logo_id = logo_upload.id if logo_upload
-
         background_upload = Upload.find_by(url: category.background_url)
-        category.uploaded_background_id = background_upload.id if background_upload
 
-        category.save!
+        category.update_columns(
+          uploaded_logo_id: logo_upload&.id,
+          uploaded_background_id: background_upload&.id
+        )
       end
     end
   end