Merge pull request #44528 from Shopify/fixtures-accessor-footprint

Reduce the memory footprint of fixtures accessors

activerecord/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   Reduce the memory footprint of fixtures accessors.
+
+    Until now fixtures accessors were eagerly defined using `define_method`.
+    So the memory usage was directly dependent of the number of fixtures and
+    test suites.
+
+    Instead fixtures accessors are now implemented with `method_missing`,
+    so they incur much less memory and CPU overhead.
+
+    *Jean Boussier*
+
 *   Fix `config.active_record.destroy_association_async_job` configuration
 
     `config.active_record.destroy_association_async_job` should allow

activerecord/lib/active_record/test_fixtures.rb

@@ -24,6 +24,7 @@ def after_teardown # :nodoc:
       class_attribute :use_instantiated_fixtures, default: false # true, false, or :no_instances
       class_attribute :pre_loaded_fixtures, default: false
       class_attribute :lock_threads, default: true
+      class_attribute :fixture_sets, default: {}
     end
 
     module ClassMethods
@@ -55,35 +56,15 @@ def fixtures(*fixture_set_names)
 
       def setup_fixture_accessors(fixture_set_names = nil)
         fixture_set_names = Array(fixture_set_names || fixture_table_names)
-        methods = Module.new do
+        unless fixture_set_names.empty?
+          self.fixture_sets = fixture_sets.dup
           fixture_set_names.each do |fs_name|
-            fs_name = fs_name.to_s
-            accessor_name = fs_name.tr("/", "_").to_sym
-
-            define_method(accessor_name) do |*fixture_names|
-              force_reload = fixture_names.pop if fixture_names.last == true || fixture_names.last == :reload
-              return_single_record = fixture_names.size == 1
-              fixture_names = @loaded_fixtures[fs_name].fixtures.keys if fixture_names.empty?
-
-              @fixture_cache[fs_name] ||= {}
-
-              instances = fixture_names.map do |f_name|
-                f_name = f_name.to_s if f_name.is_a?(Symbol)
-                @fixture_cache[fs_name].delete(f_name) if force_reload
-
-                if @loaded_fixtures[fs_name][f_name]
-                  @fixture_cache[fs_name][f_name] ||= @loaded_fixtures[fs_name][f_name].find
-                else
-                  raise StandardError, "No fixture named '#{f_name}' found for fixture set '#{fs_name}'"
-                end
-              end
-
-              return_single_record ? instances.first : instances
-            end
-            private accessor_name
+            key = fs_name.match?(%r{/}) ? -fs_name.to_s.tr("/", "_") : fs_name
+            key = -key.to_s if key.is_a?(Symbol)
+            fs_name = -fs_name.to_s if fs_name.is_a?(Symbol)
+            fixture_sets[key] = fs_name
           end
         end
-        include methods
       end
 
       def uses_transaction(*methods)
@@ -283,5 +264,42 @@ def instantiate_fixtures
       def load_instances?
         use_instantiated_fixtures != :no_instances
       end
+
+      def method_missing(name, *args, **kwargs, &block)
+        if fs_name = fixture_sets[name.to_s]
+          access_fixture(fs_name, *args, **kwargs, &block)
+        else
+          super
+        end
+      end
+
+      def respond_to_missing?(name, include_private = false)
+        if include_private && fixture_sets.key?(name.to_s)
+          true
+        else
+          super
+        end
+      end
+
+      def access_fixture(fs_name, *fixture_names)
+        force_reload = fixture_names.pop if fixture_names.last == true || fixture_names.last == :reload
+        return_single_record = fixture_names.size == 1
+
+        fixture_names = @loaded_fixtures[fs_name].fixtures.keys if fixture_names.empty?
+        @fixture_cache[fs_name] ||= {}
+
+        instances = fixture_names.map do |f_name|
+          f_name = f_name.to_s if f_name.is_a?(Symbol)
+          @fixture_cache[fs_name].delete(f_name) if force_reload
+
+          if @loaded_fixtures[fs_name][f_name]
+            @fixture_cache[fs_name][f_name] ||= @loaded_fixtures[fs_name][f_name].find
+          else
+            raise StandardError, "No fixture named '#{f_name}' found for fixture set '#{fs_name}'"
+          end
+        end
+
+        return_single_record ? instances.first : instances
+      end
   end
 end