Nested transaction for find_or_create_by! queries.

For background see
https://apidock.com/rails/v4.2.7/ActiveRecord/Relation/find_or_create_by.

app/models/user_interacted_project.rb

@@ -23,11 +23,17 @@ class UserInteractedProject < ActiveRecord::Base
       }
 
       cached_exists?(attributes) do
-        begin
+        transaction(requires_new: true) do
-          find_or_create_by!(attributes)
+          begin
-          true # not caching the whole record here for now
+            where(attributes).select(1).first || create!(attributes)
-        rescue ActiveRecord::RecordNotUnique
+            true # not caching the whole record here for now
-          retry
+          rescue ActiveRecord::RecordNotUnique
+            # Note, above queries are not atomic and prone
+            # to race conditions (similar like #find_or_create!).
+            # We retry and make sure the outer transaction (if any)
+            # is not aborted because of this.
+            retry
+          end
         end
       end
     end