Never attempt to write virtual attributes to the database

Currently the place where we limit what gets sent to the database is in
the implementation for `partial_writes`. We should also be restricting
it to column names when partial writes are turned off.

Note that we're using `&` instead of just defaulting to
`self.class.column_names`, as the instance version of `attribute_names`
does not include attributes which are uninitialized (were not included
in the select clause)

activerecord/lib/active_record/persistence.rb

@@ -701,7 +701,8 @@ def create_or_update(*args, &block)
 
     # Updates the associated record with values matching those of the instance attributes.
     # Returns the number of affected rows.
-    def _update_record(attribute_names = self.attribute_names)
+    def _update_record(attribute_names = self.column_names)
+      attribute_names &= self.class.column_names
       attributes_values = arel_attributes_with_values_for_update(attribute_names)
       if attributes_values.empty?
         rows_affected = 0
@@ -719,6 +720,7 @@ def _update_record(attribute_names = self.attribute_names)
     # Creates a record with values matching those of the instance attributes
     # and returns its id.
     def _create_record(attribute_names = self.attribute_names)
+      attribute_names &= self.class.column_names
       attributes_values = arel_attributes_with_values_for_create(attribute_names)
 
       new_id = self.class._insert_record(attributes_values)

activerecord/test/cases/dirty_test.rb

@@ -736,6 +736,25 @@ def pirate.catchphrase
     assert record.save
   end
 
+  test "virtual attributes are not written with partial_writes off" do
+    original_partial_writes = ActiveRecord::Base.partial_writes
+    begin
+      ActiveRecord::Base.partial_writes = false
+      klass = Class.new(ActiveRecord::Base) do
+        self.table_name = "people"
+        attribute :non_persisted_attribute, :string
+      end
+
+      record = klass.new(first_name: "Sean")
+      record.non_persisted_attribute_will_change!
+
+      assert_predicate record, :non_persisted_attribute_changed?
+      assert record.save
+    ensure
+      ActiveRecord::Base.partial_writes = original_partial_writes
+    end
+  end
+
   test "mutating and then assigning doesn't remove the change" do
     pirate = Pirate.create!(catchphrase: "arrrr")
     pirate.catchphrase << " matey!"