2 files changed, 35 insertions, 17 deletions
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index 4429c655a2..525ac65722 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -387,25 +387,35 @@ module ActiveRecord
           records
         end
 
-        def merge_target_lists(loaded, existing)
-          return loaded if existing.empty?
-          return existing if loaded.empty?
-
-          loaded.map do |f|
-            i = existing.index(f)
-            if i
-              existing.delete_at(i).tap do |t|
-                keys = ["id"] + t.changes.keys + (f.attribute_names - t.attribute_names)
-                # FIXME: this call to attributes causes many NoMethodErrors
-                attributes = f.attributes
-                (attributes.keys - keys).each do |k|
-                  t.send("#{k}=", attributes[k])
-                end
+        # We have some records loaded from the database (persisted) and some that are
+        # in-memory (memory). The same record may be represented in the persisted array
+        # and in the memory array.
+        #
+        # So the task of this method is to merge them according to the following rules:
+        #
+        #   * The final array must not have duplicates
+        #   * The order of the persisted array is to be preserved
+        #   * Any changes made to attributes on objects in the memory array are to be preserved
+        #   * Otherwise, attributes should have the value found in the database
+        def merge_target_lists(persisted, memory)
+          return persisted if memory.empty?
+          return memory    if persisted.empty?
+
+          persisted.map! do |record|
+            mem_record = memory.delete(record)
+
+            if mem_record
+              (record.attribute_names - mem_record.changes.keys).each do |name|
+                mem_record[name] = record[name]
               end
+
+              mem_record
             else
-              f
+              record
             end
-          end + existing
+          end
+
+          persisted + memory
         end
 
         # Do the relevant stuff to insert the given record into the association collection.
diff --git a/activerecord/lib/active_record/railties/controller_runtime.rb b/activerecord/lib/active_record/railties/controller_runtime.rb
index bc6ca936c0..9e3b3429e4 100644
--- a/activerecord/lib/active_record/railties/controller_runtime.rb
+++ b/activerecord/lib/active_record/railties/controller_runtime.rb
@@ -2,13 +2,21 @@ require 'active_support/core_ext/module/attr_internal'
 
 module ActiveRecord
   module Railties
-    module ControllerRuntime
+    module ControllerRuntime #:nodoc:
       extend ActiveSupport::Concern
 
     protected
 
       attr_internal :db_runtime
 
+      def process_action(action, *args)
+        # We also need to reset the runtime before each action
+        # because of queries in middleware or in cases we are streaming
+        # and it won't be cleaned up by the method below.
+        ActiveRecord::LogSubscriber.reset_runtime
+        super
+      end
+
       def cleanup_view_runtime
         if ActiveRecord::Base.connected?
           db_rt_before_render = ActiveRecord::LogSubscriber.reset_runtime