move the cache to the AR models and populate it on inherited

2 files changed, 31 insertions, 20 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index b06add096f..04e3dd49e7 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -18,6 +18,7 @@ require 'arel'
 require 'active_record/errors'
 require 'active_record/log_subscriber'
 require 'active_record/explain_subscriber'
+require 'active_record/relation/delegation'
 
 module ActiveRecord #:nodoc:
   # = Active Record
@@ -290,6 +291,7 @@ module ActiveRecord #:nodoc:
     extend Translation
     extend DynamicMatchers
     extend Explain
+    extend Delegation::DelegateCache
 
     include Persistence
     include ReadonlyAttributes
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 2b132d517d..31f924ba52 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -1,8 +1,33 @@
-require 'thread'
-require 'thread_safe'
+require 'active_support/concern'
 
 module ActiveRecord
   module Delegation # :nodoc:
+    module DelegateCache
+      def relation_delegate_class(klass) # :nodoc:
+        @relation_delegate_cache[klass]
+      end
+
+      def initialize_relation_delegate_cache # :nodoc:
+        @relation_delegate_cache = cache = {}
+        [
+          ActiveRecord::Relation,
+          ActiveRecord::Associations::CollectionProxy,
+          ActiveRecord::AssociationRelation
+        ].each do |klass|
+          delegate = Class.new(klass) {
+            include ActiveRecord::Relation::ClassSpecificRelation
+          }
+          const_set klass.name.gsub('::', '_'), delegate
+          cache[klass] = delegate
+        end
+      end
+
+      def inherited(child_class)
+        child_class.initialize_relation_delegate_cache
+        super
+      end
+    end
+
     extend ActiveSupport::Concern
 
     # This module creates compiled delegation methods dynamically at runtime, which makes
@@ -71,30 +96,14 @@ module ActiveRecord
     end
 
     module ClassMethods # :nodoc:
-      @@subclasses = ThreadSafe::Cache.new(:initial_capacity => 2)
-
       def create(klass, *args)
         relation_class_for(klass).new(klass, *args)
       end
 
       private
-      # Cache the constants in @@subclasses because looking them up via const_get
-      # make instantiation significantly slower.
-      def relation_class_for(klass)
-        klass_name = klass.name
-
-        if klass_name
-          my_cache = @@subclasses.compute_if_absent(self) { ThreadSafe::Cache.new }
-          # This hash is keyed by klass.name to avoid memory leaks in development mode
-          my_cache.compute_if_absent(klass_name) do
-            # Cache#compute_if_absent guarantees that the block will only executed once for the given klass_name
-            subclass_name = "#{name.gsub('::', '_')}_#{klass_name.gsub('::', '_')}"
 
-            const_set(subclass_name, Class.new(self) { include ClassSpecificRelation })
-          end
-        else
-          self
-        end
+      def relation_class_for(klass)
+        klass.relation_delegate_class(self)
       end
     end