Add Model.lock and relation#lock now that arel has locking

activerecord/CHANGELOG

@@ -1,5 +1,12 @@
 *Edge*
 
+* Add .lock finder method [Pratik Naik]
+
+  User.lock.where(:name => 'lifo').to_a
+
+  old_items = Item.where("age > 100")
+  old_items.locked.each {|i| .. }
+
 * Add Model.from and association_collection#from finder methods [Pratik Naik]
 
   user = User.scoped

activerecord/lib/active_record/associations/association_collection.rb

@@ -21,7 +21,7 @@ module ActiveRecord
         construct_sql
       end
 
-      delegate :group, :order, :limit, :joins, :where, :preload, :eager_load, :from, :to => :scoped
+      delegate :group, :order, :limit, :joins, :where, :preload, :eager_load, :from, :lock, :to => :scoped
 
       def select(select = nil, &block)
         if block_given?

activerecord/lib/active_record/base.rb

@@ -652,7 +652,7 @@ module ActiveRecord #:nodoc:
         end
       end
 
-      delegate :select, :group, :order, :limit, :joins, :where, :preload, :eager_load, :from, :to => :scoped
+      delegate :select, :group, :order, :limit, :joins, :where, :preload, :eager_load, :from, :lock, :to => :scoped
 
       # A convenience wrapper for <tt>find(:first, *args)</tt>. You can pass in all the
       # same arguments to this method as you can to <tt>find(:first)</tt>.
@@ -1573,6 +1573,9 @@ module ActiveRecord #:nodoc:
             offset(construct_offset(options[:offset], scope)).
             from(options[:from])
 
+          lock = (scope && scope[:lock]) || options[:lock]
+          relation = relation.lock if lock.present?
+
           relation = relation.readonly if options[:readonly]
 
           relation

activerecord/lib/active_record/relation.rb

@@ -55,6 +55,17 @@ module ActiveRecord
       orders.present? ? create_new_relation(@relation.order(orders)) : create_new_relation
     end
 
+    def lock(locks = true)
+      case locks
+      when String
+        create_new_relation(@relation.lock(locks))
+      when TrueClass, NilClass
+        create_new_relation(@relation.lock)
+      else
+        create_new_relation
+      end
+    end
+
     def reverse_order
       relation = create_new_relation
       relation.instance_variable_set(:@orders, nil)