This patch changes update_attribute implementatino so:

- it will only save the attribute it has been asked to save and not all dirty attributes

- it does not invoke callbacks

- it does change updated_at/on

Signed-off-by: José Valim <jose.valim@gmail.com>

activerecord/lib/active_record/persistence.rb

@@ -102,12 +102,19 @@ module ActiveRecord
       became
     end
 
-    # Updates a single attribute and saves the record without going through the normal validation procedure.
-    # This is especially useful for boolean flags on existing records. The regular +update_attribute+ method
-    # in Base is replaced with this when the validations module is mixed in, which it is by default.
+    # Updates a single attribute and saves the record without going through the normal validation procedure
+    # or callbacks. This is especially useful for boolean flags on existing records.
     def update_attribute(name, value)
       send("#{name}=", value)
-      save(:validate => false)
+      primary_key = self.class.primary_key
+      h = {name => value}
+      if should_record_update_timestamps
+        self.send(:record_update_timestamps)
+        current_time = current_time_from_proper_timezone
+        timestamp_attributes_for_update_in_model.each { |column| h.merge!(column => current_time) }
+      end
+      self.class.update_all(h, {primary_key => self[primary_key]}) == 1
+      @changed_attributes.delete(name.to_s)
     end
 
     # Updates all the attributes from the passed-in Hash and saves the record. 

activerecord/lib/active_record/timestamp.rb

@@ -58,14 +58,22 @@ module ActiveRecord
     end
 
     def update(*args) #:nodoc:
-      if record_timestamps && (!partial_updates? || changed?)
+      record_update_timestamps
+      super
+    end
+
+    def record_update_timestamps
+      if should_record_update_timestamps
         current_time = current_time_from_proper_timezone
         timestamp_attributes_for_update_in_model.each { |column| write_attribute(column.to_s, current_time) }
       end
-
-      super
     end
 
+    def should_record_update_timestamps
+      record_timestamps && (!partial_updates? || changed?)
+    end
+
+
     def timestamp_attributes_for_update #:nodoc:
       [:updated_at, :updated_on]
     end

activerecord/test/cases/base_test.rb

@@ -893,6 +893,46 @@ class BasicsTest < ActiveRecord::TestCase
     assert !Topic.find(1).approved?
   end
 
+  def test_update_attribute_with_one_changed_and_one_updated
+    t = Topic.order('id').limit(1).first
+    title, author_name = t.title, t.author_name
+    t.author_name = 'John'
+    t.update_attribute(:title, 'super_title')
+    assert_equal 'John', t.author_name
+    assert_equal 'super_title', t.title
+    assert t.changed?, "topic should have changed"
+    assert t.author_name_changed?, "author_name should have changed"
+    assert !t.title_changed?, "title should not have changed"
+    assert_nil t.title_change, 'title change should be nil'
+    assert_equal ['author_name'], t.changed
+
+    t.reload
+    assert_equal 'David', t.author_name
+    assert_equal 'super_title', t.title
+  end
+
+  def test_update_attribute_with_one_updated
+    t = Topic.first
+    title = t.title
+    t.update_attribute(:title, 'super_title')
+    assert_equal 'super_title', t.title
+    assert !t.changed?, "topic should not have changed"
+    assert !t.title_changed?, "title should not have changed"
+    assert_nil t.title_change, 'title change should be nil'
+
+    t.reload
+    assert_equal 'super_title', t.title
+  end
+
+  def test_update_attribute_for_udpated_at_on
+    developer = Developer.find(1)
+    updated_at = developer.updated_at
+    developer.update_attribute(:salary, 80001)
+    assert_not_equal updated_at, developer.updated_at
+    developer.reload
+    assert_not_equal updated_at, developer.updated_at
+  end
+
   def test_update_attributes
     topic = Topic.find(1)
     assert !topic.approved?

activerecord/test/cases/dirty_test.rb

@@ -475,10 +475,9 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.find_by_catchphrase("Ahoy!")
     pirate.update_attribute(:catchphrase, "Ninjas suck!")
 
-    assert_equal 2, pirate.previous_changes.size
-    assert_equal ["Ahoy!", "Ninjas suck!"], pirate.previous_changes['catchphrase']
-    assert_not_nil pirate.previous_changes['updated_on'][0]
-    assert_not_nil pirate.previous_changes['updated_on'][1]
+    assert_equal 0, pirate.previous_changes.size
+    assert_nil pirate.previous_changes['catchphrase']
+    assert_nil pirate.previous_changes['updated_on']
     assert !pirate.previous_changes.key?('parrot_id')
     assert !pirate.previous_changes.key?('created_on')    
   end

activerecord/test/cases/nested_attributes_test.rb

@@ -195,7 +195,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
     [1, '1', true, 'true'].each do |truth|
       @pirate.reload.create_ship(:name => 'Mister Pablo')
       assert_difference('Ship.count', -1) do
-        @pirate.update_attribute(:ship_attributes, { :id => @pirate.ship.id, :_destroy => truth })
+        @pirate.update_attributes(:ship_attributes => { :id => @pirate.ship.id, :_destroy => truth })
       end
     end
   end
@@ -203,7 +203,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_not_destroy_an_existing_record_if_destroy_is_not_truthy
     [nil, '0', 0, 'false', false].each do |not_truth|
       assert_no_difference('Ship.count') do
-        @pirate.update_attribute(:ship_attributes, { :id => @pirate.ship.id, :_destroy => not_truth })
+        @pirate.update_attributes(:ship_attributes => { :id => @pirate.ship.id, :_destroy => not_truth })
       end
     end
   end
@@ -212,7 +212,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
     Pirate.accepts_nested_attributes_for :ship, :allow_destroy => false, :reject_if => proc { |attributes| attributes.empty? }
 
     assert_no_difference('Ship.count') do
-      @pirate.update_attribute(:ship_attributes, { :id => @pirate.ship.id, :_destroy => '1' })
+      @pirate.update_attributes(:ship_attributes => { :id => @pirate.ship.id, :_destroy => '1' })
     end
 
     Pirate.accepts_nested_attributes_for :ship, :allow_destroy => true, :reject_if => proc { |attributes| attributes.empty? }
@@ -247,13 +247,13 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   end
 
   def test_should_accept_update_only_option
-    @pirate.update_attribute(:update_only_ship_attributes, { :id => @pirate.ship.id, :name => 'Mayflower' })
+    @pirate.update_attributes(:update_only_ship_attributes => { :id => @pirate.ship.id, :name => 'Mayflower' })
   end
 
   def test_should_create_new_model_when_nothing_is_there_and_update_only_is_true
     @ship.delete
     assert_difference('Ship.count', 1) do
-      @pirate.reload.update_attribute(:update_only_ship_attributes, { :name => 'Mayflower' })
+      @pirate.reload.update_attributes(:update_only_ship_attributes => { :name => 'Mayflower' })
     end
   end
 
@@ -353,7 +353,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
     [1, '1', true, 'true'].each do |truth|
       @ship.reload.create_pirate(:catchphrase => 'Arr')
       assert_difference('Pirate.count', -1) do
-        @ship.update_attribute(:pirate_attributes, { :id => @ship.pirate.id, :_destroy => truth })
+        @ship.update_attributes(:pirate_attributes => { :id => @ship.pirate.id, :_destroy => truth })
       end
     end
   end
@@ -361,7 +361,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
   def test_should_not_destroy_an_existing_record_if_destroy_is_not_truthy
     [nil, '0', 0, 'false', false].each do |not_truth|
       assert_no_difference('Pirate.count') do
-        @ship.update_attribute(:pirate_attributes, { :id => @ship.pirate.id, :_destroy => not_truth })
+        @ship.update_attributes(:pirate_attributes => { :id => @ship.pirate.id, :_destroy => not_truth })
       end
     end
   end
@@ -370,7 +370,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
     Ship.accepts_nested_attributes_for :pirate, :allow_destroy => false, :reject_if => proc { |attributes| attributes.empty? }
 
     assert_no_difference('Pirate.count') do
-      @ship.update_attribute(:pirate_attributes, { :id => @ship.pirate.id, :_destroy => '1' })
+      @ship.update_attributes(:pirate_attributes => { :id => @ship.pirate.id, :_destroy => '1' })
     end
 
     Ship.accepts_nested_attributes_for :pirate, :allow_destroy => true, :reject_if => proc { |attributes| attributes.empty? }
@@ -398,7 +398,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
   def test_should_create_new_model_when_nothing_is_there_and_update_only_is_true
     @pirate.delete
     assert_difference('Pirate.count', 1) do
-      @ship.reload.update_attribute(:update_only_pirate_attributes, { :catchphrase => 'Arr' })
+      @ship.reload.update_attributes(:update_only_pirate_attributes => { :catchphrase => 'Arr' })
     end
   end