4 files changed, 28 insertions, 5 deletions
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activerecord/lib/active_record/attribute_set.rb
index 8f6b73eac2..5e5f7ca1b5 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activerecord/lib/active_record/attribute_set.rb
@@ -6,10 +6,6 @@ module ActiveRecord
       @attributes = attributes
     end
 
-    def update(other)
-      attributes.update(other.attributes)
-    end
-
     def to_hash
       attributes.each_with_object({}) { |(k, v), h| h[k] = v.value }
     end
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 6707f12489..86cc928644 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -395,7 +395,7 @@ module ActiveRecord
           self.class.unscoped { self.class.find(id) }
         end
 
-      @attributes.update(fresh_object.instance_variable_get('@attributes'))
+      @attributes = fresh_object.instance_variable_get('@attributes')
 
       @column_types = self.class.column_types
       self
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 84a7a8ef68..7566af920f 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -842,6 +842,26 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert_not @target.attribute_method?(:title)
   end
 
+  def test_attribute_names_on_new_record
+    model = @target.new
+
+    assert_equal @target.column_names, model.attribute_names
+  end
+
+  def test_attribute_names_on_queried_record
+    model = @target.last!
+
+    assert_equal @target.column_names, model.attribute_names
+  end
+
+  def test_attribute_names_with_custom_select
+    model = @target.select('id').last!
+
+    assert_equal ['id'], model.attribute_names
+    # Sanity check, make sure other columns exist
+    assert_not_equal ['id'], @target.column_names
+  end
+
   private
 
   def new_topic_like_ar_class(&block)
diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 28341d0b42..1192ecd6b4 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -858,4 +858,11 @@ class PersistenceTest < ActiveRecord::TestCase
       post.body
     end
   end
+
+  def test_reload_removes_custom_selects
+    post = Post.select('posts.*, 1 as wibble').last!
+
+    assert_equal 1, post[:wibble]
+    assert_nil post.reload[:wibble]
+  end
 end