Partial updates don't update lock_version if nothing changed. [#426 state:resolved]

activerecord/CHANGELOG

 *Edge*
 
+* Partial updates don't update lock_version if nothing changed.  #426 [Daniel Morrison]
+
 * Fix column collision with named_scope and :joins.  #46 [Duncan Beevers, Mark Catley]
 
 * db:migrate:down and :up update schema_migrations.  #369 [Michael Raidel, RaceCondition]

activerecord/lib/active_record/locking/optimistic.rb

@@ -68,6 +68,7 @@ def attributes_from_column_definition_with_lock
 
         def update_with_lock(attribute_names = @attributes.keys) #:nodoc:
           return update_without_lock(attribute_names) unless locking_enabled?
+          return 0 if attribute_names.empty?
 
           lock_col = self.class.locking_column
           previous_value = send(lock_col).to_i

activerecord/test/cases/dirty_test.rb

@@ -2,6 +2,7 @@
 require 'models/topic'    # For booleans
 require 'models/pirate'   # For timestamps
 require 'models/parrot'
+require 'models/person'   # For optimistic locking
 
 class Pirate # Just reopening it, not defining it
   attr_accessor :detected_changes_in_after_update # Boolean for if changes are detected
@@ -125,6 +126,24 @@ def test_partial_update
     end
   end
 
+  def test_partial_update_with_optimistic_locking
+    person = Person.new(:first_name => 'foo')
+    old_lock_version = 1
+
+    with_partial_updates Person, false do
+      assert_queries(2) { 2.times { person.save! } }
+      Person.update_all({ :first_name => 'baz' }, :id => person.id)
+    end
+
+    with_partial_updates Person, true do
+      assert_queries(0) { 2.times { person.save! } }
+      assert_equal old_lock_version, person.reload.lock_version
+
+      assert_queries(1) { person.first_name = 'bar'; person.save! }
+      assert_not_equal old_lock_version, person.reload.lock_version
+    end
+  end
+
   def test_changed_attributes_should_be_preserved_if_save_failure
     pirate = Pirate.new
     pirate.parrot_id = 1

activerecord/test/cases/locking_test.rb

@@ -29,10 +29,12 @@ def test_lock_existing
     assert_equal 0, p1.lock_version
     assert_equal 0, p2.lock_version
 
+    p1.first_name = 'stu'
     p1.save!
     assert_equal 1, p1.lock_version
     assert_equal 0, p2.lock_version
 
+    p2.first_name = 'sue'
     assert_raises(ActiveRecord::StaleObjectError) { p2.save! }
   end
 
@@ -42,11 +44,14 @@ def test_lock_repeating
     assert_equal 0, p1.lock_version
     assert_equal 0, p2.lock_version
 
+    p1.first_name = 'stu'
     p1.save!
     assert_equal 1, p1.lock_version
     assert_equal 0, p2.lock_version
 
+    p2.first_name = 'sue'
     assert_raises(ActiveRecord::StaleObjectError) { p2.save! }
+    p2.first_name = 'sue2'
     assert_raises(ActiveRecord::StaleObjectError) { p2.save! }
   end
 
@@ -54,15 +59,18 @@ def test_lock_new
     p1 = Person.new(:first_name => 'anika')
     assert_equal 0, p1.lock_version
 
+    p1.first_name = 'anika2'
     p1.save!
     p2 = Person.find(p1.id)
     assert_equal 0, p1.lock_version
     assert_equal 0, p2.lock_version
 
+    p1.first_name = 'anika3'
     p1.save!
     assert_equal 1, p1.lock_version
     assert_equal 0, p2.lock_version
 
+    p2.first_name = 'sue'
     assert_raises(ActiveRecord::StaleObjectError) { p2.save! }
   end
 
@@ -81,10 +89,12 @@ def test_lock_column_name_existing
     assert_equal 0, t1.version
     assert_equal 0, t2.version
 
+    t1.tps_report_number = 700
     t1.save!
     assert_equal 1, t1.version
     assert_equal 0, t2.version
 
+    t2.tps_report_number = 800
     assert_raises(ActiveRecord::StaleObjectError) { t2.save! }
   end
 
@@ -93,6 +103,7 @@ def test_lock_column_is_mass_assignable
     assert_equal 0, p1.lock_version
     assert_equal p1.lock_version, Person.new(p1.attributes).lock_version
 
+    p1.first_name = 'bianca2'
     p1.save!
     assert_equal 1, p1.lock_version
     assert_equal p1.lock_version, Person.new(p1.attributes).lock_version
@@ -146,6 +157,15 @@ def test_quote_table_name
     assert ref.save
   end
 
+  # Useful for partial updates, don't only update the lock_version if there
+  # is nothing else being updated.
+  def test_update_without_attributes_does_not_only_update_lock_version
+    assert_nothing_raised do
+      p1 = Person.new(:first_name => 'anika')
+      p1.send(:update_with_lock, [])
+    end
+  end
+
   private
 
     def add_counter_column_to(model)