1 files changed, 21 insertions, 21 deletions
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 175019a72b..7a050ca224 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -1,3 +1,4 @@
+require 'active_support/core_ext/string/filters'
 
 module ActiveRecord
   # = Active Record Has Many Through Association
@@ -12,21 +13,6 @@ module ActiveRecord
         @through_association = nil
       end
 
-      # Returns the size of the collection by executing a SELECT COUNT(*) query
-      # if the collection hasn't been loaded, and by calling collection.size if
-      # it has. If the collection will likely have a size greater than zero,
-      # and if fetching the collection will be needed afterwards, one less
-      # SELECT query will be generated by using #length instead.
-      def size
-        if has_cached_counter?
-          owner.read_attribute cached_counter_attribute_name(reflection)
-        elsif loaded?
-          target.size
-        else
-          super
-        end
-      end
-
       def concat(*records)
         unless owner.new_record?
           records.flatten.each do |record|
@@ -63,7 +49,16 @@ module ActiveRecord
         end
 
         save_through_record(record)
-        update_counter(1)
+        if has_cached_counter? && !through_reflection_updates_counter_cache?
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Automatic updating of counter caches on through associations has been
+            deprecated, and will be removed in Rails 5. Instead, please set the
+            appropriate `counter_cache` options on the `has_many` and `belongs_to`
+            for your associations to #{through_reflection.name}.
+          MSG
+
+          update_counter_in_database(1)
+        end
         record
       end
 
@@ -93,7 +88,9 @@ module ActiveRecord
         end
 
         def through_scope_attributes
-          scope.where_values_hash(through_association.reflection.name.to_s).except!(through_association.reflection.foreign_key)
+          scope.where_values_hash(through_association.reflection.name.to_s).
+            except!(through_association.reflection.foreign_key,
+                    through_association.reflection.klass.inheritance_column)
         end
 
         def save_through_record(record)
@@ -149,13 +146,11 @@ module ActiveRecord
             if scope.klass.primary_key
               count = scope.destroy_all.length
             else
-              scope.to_a.each do |record|
-                record.run_callbacks :destroy
-              end
+              scope.each(&:_run_destroy_callbacks)
 
               arel = scope.arel
 
-              stmt = Arel::DeleteManager.new arel.engine
+              stmt = Arel::DeleteManager.new
               stmt.from scope.klass.arel_table
               stmt.wheres = arel.constraints
 
@@ -216,6 +211,11 @@ module ActiveRecord
         def invertible_for?(record)
           false
         end
+
+        def through_reflection_updates_counter_cache?
+          counter_name = cached_counter_attribute_name
+          inverse_updates_counter_named?(counter_name, through_reflection)
+        end
     end
   end
 end