ActiveRecord::Associations::CollectionProxy#new の性能劣化を回復させる危険な闇patch

ar_collection_proxy_delegates_to_association.patch

diff --git activerecord/lib/active_record/associations/collection_proxy.rb activerecord/lib/active_record/associations/collection_proxy.rb
index a034753..c5b84e5 100644
--- activerecord/lib/active_record/associations/collection_proxy.rb
+++ activerecord/lib/active_record/associations/collection_proxy.rb
@@ -28,13 +28,23 @@ module ActiveRecord
     # is computed directly through SQL and does not trigger by itself the
     # instantiation of the actual post records.
     class CollectionProxy < Relation
+
       delegate(*(ActiveRecord::Calculations.public_instance_methods - [:count]), to: :scope)
       delegate :find_nth, to: :scope
+      delegate :merge!, to: :scope
+
+      delegate(*(VALUE_METHODS.map{|name| "#{name}_values="}), to: :scope)
+      delegate(*((VALUE_METHODS - [:create_with]).map{|name| "#{name}_values"}), to: :scope)

       def initialize(klass, association) #:nodoc:
         @association = association
         super klass, klass.arel_table
-        merge! association.scope(nullify: false)
+
+        if scope = association.reflection.scope
+          rel = association.klass.unscoped.instance_exec(association.owner, &scope)
+          self.extend(*rel.extending_values) unless rel.extending_values.blank?
+        end
+        Array.wrap(association.options[:extend]).each { |ext| proxy_extend(ext) }
       end

       def target
diff --git activerecord/lib/active_record/relation/merger.rb activerecord/lib/active_record/relation/merger.rb
index a27f990..23b3e27 100644
--- activerecord/lib/active_record/relation/merger.rb
+++ activerecord/lib/active_record/relation/merger.rb
@@ -121,10 +121,10 @@ module ActiveRecord
         relation.where_values = where_values
         relation.bind_values  = bind_values

-        if other.reordering_value
+        if other.reordering_value.present?
           # override any order specified in the original relation
           relation.reorder! other.order_values
-        elsif other.order_values
+        elsif other.order_values.present?
           # merge in order_values from relation
           relation.order! other.order_values
         end