Base.update_all :order and :limit options. Useful for MySQL updates that must be ordered to avoid violating unique constraints.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6440 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Base.update_all :order and :limit options. Useful for MySQL updates that must be ordered to avoid violating unique constraints.  [Jeremy Kemper]
+
 * Remove deprecated object transactions.  People relying on this functionality should install the object_transactions plugin at http://code.bitsweat.net/svn/object_transactions.  Closes #5637 [Koz, Jeremy Kemper]
 
 * PostgreSQL: remove DateTime -> Time downcast. Warning: do not enable translate_results for the C bindings if you have timestamps outside Time's domain.  [Jeremy Kemper]

activerecord/lib/active_record/base.rb

@@ -501,9 +501,15 @@ module ActiveRecord #:nodoc:
       # Updates all records with the SET-part of an SQL update statement in +updates+ and returns an integer with the number of rows updated.
       # A subset of the records can be selected by specifying +conditions+. Example:
       #   Billing.update_all "category = 'authorized', approved = 1", "author = 'David'"
-      def update_all(updates, conditions = nil)
+      #
+      # Optional :order and :limit options may be given as the third parameter,
+      # but their behavior is database-specific.
+      def update_all(updates, conditions = nil, options = {})
         sql  = "UPDATE #{table_name} SET #{sanitize_sql_for_assignment(updates)} "
-        add_conditions!(sql, conditions, scope(:find))
+        scope = scope(:find)
+        add_conditions!(sql, conditions, scope)
+        add_order!(sql, options[:order], scope)
+        add_limit!(sql, options, scope)
         connection.update(sql, "#{name} Update")
       end
 

activerecord/test/base_test.rb

@@ -569,6 +569,12 @@ class BasicsTest < Test::Unit::TestCase
     end
   end
 
+  if current_adapter?(:MysqlAdapter)
+    def test_update_all_with_order_and_limit
+      assert_equal 1, Topic.update_all("content = 'bulk updated!'", nil, :limit => 1, :order => 'id DESC')
+    end
+  end
+
   def test_update_many
     topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" } }
     updated = Topic.update(topic_data.keys, topic_data.values)