Add method to retrieve translations in one database query

This methods performs much better when we need to load a lot of
globalized models translations and returns the best fallback translation
for the current language.

app/models/concerns/globalizable.rb

@@ -100,5 +100,22 @@ module Globalizable
     def translation_class_delegate(method)
       translation_class.instance_eval { delegate method, to: :globalized_model }
     end
+
+    def with_fallback_translation
+      translations_foreign_key = reflect_on_association(:translations).foreign_key
+      fallbacks = Globalize.fallbacks(Globalize.locale)
+
+      fallbacks_with_order = fallbacks.map.with_index do |locale, order|
+        "('#{locale}', #{order})"
+      end.join(", ")
+
+      translations_ids = translation_class
+        .select("DISTINCT ON (#{translations_foreign_key}) id")
+        .where(locale: fallbacks)
+        .joins("LEFT JOIN (VALUES #{fallbacks_with_order}) AS locales(name, ordering) ON locale = locales.name")
+        .order(translations_foreign_key, "locales.ordering")
+
+      with_translations(fallbacks).where("#{translations_table_name}.id": translations_ids)
+    end
   end
 end