Migrate data

So it turns out all images uploaded before the ActiveStorage migration are internally set to "public-read", and all images uploaded after the migration are internally set to "private". This migration switches all images in S3 buckets back to "public-read".

db/migrate/20230504001141_public_images.rb

@@ -0,0 +1,40 @@
+require 'aws-sdk-s3'
+
+class PublicImages < ActiveRecord::Migration[7.0]
+  def up
+    return unless s3_bucket
+
+    check_connection!
+    set_objects_to_readable
+
+    ActiveStorage::Blob.
+      where(service_name: "amazon").
+      where("content_type LIKE 'image/%'").
+      update_all(service_name: "amazon_public")
+  end
+
+  def down
+    ActiveStorage::Blob.
+      where(service_name: "amazon_public").
+      where("content_type LIKE 'image/%'").
+      update_all(service_name: "amazon")
+  end
+
+  private
+
+  # Returns an Aws::S3::Bucket object
+  def s3_bucket
+    @s3_bucket ||= ActiveStorage::Blob.where(service_name: "amazon").first&.service&.bucket
+  end
+
+  # Checks bucket status. Throws an error if connection fails
+  def check_connection!
+    s3_bucket.exists?
+  end
+
+  # Sets bucket objects' ACL to "public-read". Performs batched processing internally
+  # with a custom enumerator, see AWS::Resources::Collection#each for details.
+  def set_objects_to_readable
+    s3_bucket.objects.each{|object| object.acl.put(acl: "public-read") }
+  end
+end