Merge pull request #695 from Cygnetise/memory_optimisations

Reduce the retained memory when defining the relation readers

core/lib/rom/plugins/relation/registry_reader.rb

@@ -14,12 +14,8 @@ class RegistryReader < ::Module
         EMPTY_REGISTRY = RelationRegistry.build(EMPTY_HASH).freeze
 
         # @api private
-        attr_reader :relations
-
-        # @api private
-        def initialize(relations:)
-          @relations = relations
-          define_readers!
+        def initialize(klass:, relation_readers_module:)
+          klass.include relation_readers_module
         end
 
         # @api private
@@ -29,15 +25,6 @@ def included(klass)
 
           klass.option :__registry__, default: -> { EMPTY_REGISTRY }
         end
-
-        private
-
-        # @api private
-        def define_readers!
-          relations.each do |name|
-            define_method(name) { __registry__[name] }
-          end
-        end
       end
     end
   end

core/lib/rom/setup/finalize/finalize_relations.rb

@@ -9,6 +9,18 @@ class Finalize
     class FinalizeRelations
       attr_reader :notifications
 
+      module BuildRelationReaders
+        def self.build(relations)
+          Module.new do
+            relations.each do |name|
+              define_method(name) do
+                __registry__[name]
+              end
+            end
+          end
+        end
+      end
+
       # Build relation registry of specified descendant classes
       #
       # This is used by the setup
@@ -30,6 +42,7 @@ def initialize(gateways, relation_classes, notifications:, mappers: nil, plugins
       # @api private
       def run!
         relation_registry = RelationRegistry.new do |registry, relations|
+          relation_readers_module = BuildRelationReaders.build(relation_names)
           @relation_classes.each do |klass|
             unless klass.adapter
               raise MissingAdapterIdentifierError,
@@ -43,7 +56,7 @@ def run!
                     "Relation with name #{key.inspect} registered more than once"
             end
 
-            klass.use(:registry_reader, relations: relation_names)
+            klass.use(:registry_reader, klass: klass, relation_readers_module: relation_readers_module)
 
             notifications.trigger('configuration.relations.class.ready', relation: klass, adapter: klass.adapter)
 

repository/lib/rom/repository/relation_reader.rb

@@ -4,27 +4,50 @@ module ROM
   class Repository
     # @api private
     class RelationReader < Module
+      extend Dry::Core::ClassAttributes
+
       # @api private
       attr_reader :klass
 
       # @api private
       attr_reader :relations
 
+      defines :relation_readers
+
+      defines :mutex
+      mutex(Mutex.new)
+
+      defines :relation_cache
+      relation_cache(Concurrent::Hash.new)
+
       module InstanceMethods
         # @api private
         def set_relation(name)
           container
             .relations[name]
-            .with(auto_struct: auto_struct)
-            .struct_namespace(struct_namespace)
+            .with(auto_struct: auto_struct, struct_namespace: struct_namespace)
+        end
+
+        def relation_reader(name, relation_cache)
+          key = [name, auto_struct, struct_namespace]
+          relation_cache[key] ||= set_relation(name)
         end
       end
 
+      # @api private
+      def mutex
+        ROM::Repository::RelationReader.mutex
+      end
+
       # @api private
       def initialize(klass, relations)
-        @klass = klass
         @relations = relations
-        define_readers!
+        mutex.synchronize do
+          unless self.class.relation_readers
+            self.class.relation_readers(build_relation_readers(relations, self.class.relation_cache))
+          end
+        end
+        klass.include self.class.relation_readers
       end
 
       # @api private
@@ -33,13 +56,16 @@ def included(klass)
         klass.include(InstanceMethods)
       end
 
+
       private
 
       # @api private
-      def define_readers!
-        relations.each do |name|
-          define_method(name) do
-            @relations[name] ||= set_relation(name)
+      def build_relation_readers(relations, relation_cache)
+        Module.new do
+          relations.each do |name|
+            define_method(name) do
+              relation_reader(name, relation_cache)
+            end
           end
         end
       end