TIL item proxies can read from the cache in bulk

app/models/item/proxy.rb

@@ -23,14 +23,6 @@ class Item
       end
     end
 
-    def cached?(type, name)
-      # TODO: is there a way to cache nil? Right now we treat is as a miss.
-      # We eagerly read the cache rather than just check if the value exists,
-      # which will usually cut down on cache requests.
-      @known_outputs[type][name] ||= Rails.cache.read(fragment_key(type, name))
-      !@known_outputs[type][name].nil?
-    end
-
     def owned?
       @owned
     end
@@ -44,6 +36,16 @@ class Item
       @wanted
     end
 
+    def fragment_key(type, name)
+      prefix = type == :partial ? 'views/' : ''
+      base = localize_fragment_key("items/#{@id}##{name}", I18n.locale)
+      prefix + base
+    end
+
+    def set_known_output(type, name, value)
+      @known_outputs[type][name] = value
+    end
+
     private
 
     def cache_method(method_name, *args, &block)
@@ -58,11 +60,5 @@ class Item
     def item
       @item ||= Item.find(@id)
     end
-
-    def fragment_key(type, name)
-      prefix = type == :partial ? 'views/' : ''
-      base = localize_fragment_key("items/#{@id}##{name}", I18n.locale)
-      prefix + base
-    end
   end
 end

app/models/item/proxy_array.rb

@@ -27,11 +27,21 @@ class Item
     private
 
     def prepare(type, name)
-      missed_proxies_by_id = self.
-        reject { |p| p.cached?(type, name) }.
-        index_by(&:id)
       item_scope = SCOPES[type][name]
       raise "unexpected #{type} #{name.inspect}" unless item_scope
+
+      # Try to read all values from the cache in one go, setting the proxy
+      # values as we go along. Delete successfully set proxies, so that
+      # everything left in proxies_by_key in the end is known to be a miss.
+      proxies_by_key = {}
+      self.each { |p| proxies_by_key[p.fragment_key(type, name)] = p }
+      Rails.cache.read_multi(*proxies_by_key.keys).each { |k, v|
+        proxies_by_key.delete(k).set_known_output(type, name, v)
+      }
+
+      missed_proxies = proxies_by_key.values
+      missed_proxies_by_id = missed_proxies.index_by(&:id)
+
       item_scope.find(missed_proxies_by_id.keys).each do |item|
         missed_proxies_by_id[item.id].item = item
       end