Fix an N+1 in avatar URLs

This is tricky: the query was being run in
`ObjectStorage::Extension::RecordsUploads#retrieve_from_store!`, but we can't
just add batch loading there, because the `#upload=` method there would use the
result immediately, making the batch only have one item.

Instead, we can pre-emptively add an item to the batch whenever an avatarable
object is initialized, and then reuse that batch item in
`#retrieve_from_store!`. However, this also has problems:

1. There is a lot of logic in `Avatarable#retrieve_upload_from_batch`.
2. Some of that logic constructs a 'fake' model for the batch key. This should
   be fine, because of ActiveRecord's override of `#==`, but it relies on that
   staying the same.

1 files changed, 2 insertions, 2 deletions

diff --git a/app/uploaders/object_storage.rb b/app/uploaders/object_storage.rb
index 3bb2e1ea63a..5aa1bc7227c 100644
--- a/app/uploaders/object_storage.rb
+++ b/app/uploaders/object_storage.rb
@@ -33,7 +33,7 @@ module ObjectStorage
 
         unless current_upload_satisfies?(paths, model)
           # the upload we already have isn't right, find the correct one
-          self.upload = uploads.find_by(model: model, path: paths)
+          self.upload = model&.retrieve_upload(identifier, paths)
         end
 
         super
@@ -46,7 +46,7 @@ module ObjectStorage
       end
 
       def upload=(upload)
-        return unless upload
+        return if upload.nil?
 
         self.object_store = upload.store
         super