2 files changed, 48 insertions, 20 deletions
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index e643c0d437..a3412582fa 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -40,11 +40,13 @@ module ActiveRecord
     # This locking mechanism will function inside a single Ruby process. To make it work across all
     # web requests, the recommended approach is to add +lock_version+ as a hidden field to your form.
     #
-    # You must ensure that your database schema defaults the +lock_version+ column to 0.
-    #
     # This behavior can be turned off by setting <tt>ActiveRecord::Base.lock_optimistically = false</tt>.
-    # To override the name of the +lock_version+ column, invoke the <tt>set_locking_column</tt> method.
-    # This method uses the same syntax as <tt>set_table_name</tt>
+    # To override the name of the +lock_version+ column, set the <tt>locking_column</tt> class attribute:
+    #
+    #   class Person < ActiveRecord::Base
+    #     self.locking_column = :lock_person
+    #   end
+    #
     module Optimistic
       extend ActiveSupport::Concern
 
@@ -82,7 +84,7 @@ module ActiveRecord
               relation.table[self.class.primary_key].eq(id).and(
                 relation.table[lock_col].eq(quote_value(previous_lock_value))
               )
-            ).arel.compile_update(arel_attributes_values(false, false, attribute_names))
+            ).arel.compile_update(arel_attributes_with_values_for_update(attribute_names))
 
             affected_rows = connection.update stmt
 
@@ -99,24 +101,29 @@ module ActiveRecord
           end
         end
 
-        def destroy #:nodoc:
-          return super unless locking_enabled?
+        def destroy_row
+          affected_rows = super
+
+          if locking_enabled? && affected_rows != 1
+            raise ActiveRecord::StaleObjectError.new(self, "destroy")
+          end
 
-          if persisted?
-            table = self.class.arel_table
-            lock_col = self.class.locking_column
-            predicate = table[self.class.primary_key].eq(id).
-              and(table[lock_col].eq(send(lock_col).to_i))
+          affected_rows
+        end
 
-            affected_rows = self.class.unscoped.where(predicate).delete_all
+        def relation_for_destroy
+          relation = super
 
-            unless affected_rows == 1
-              raise ActiveRecord::StaleObjectError.new(self, "destroy")
-            end
+          if locking_enabled?
+            column_name = self.class.locking_column
+            column      = self.class.columns_hash[column_name]
+            substitute  = connection.substitute_at(column, relation.bind_values.length)
+
+            relation = relation.where(self.class.arel_table[column_name].eq(substitute))
+            relation.bind_values << [column, self[column_name].to_i]
           end
 
-          @destroyed = true
-          freeze
+          relation
         end
 
       module ClassMethods
@@ -131,8 +138,7 @@ module ActiveRecord
 
         # Set the column to use for optimistic locking. Defaults to +lock_version+.
         def locking_column=(value)
-          @original_locking_column = @locking_column if defined?(@locking_column)
-          @locking_column          = value.to_s
+          @locking_column = value.to_s
         end
 
         # The version column used for optimistic locking. Defaults to +lock_version+.
diff --git a/activerecord/lib/active_record/locking/pessimistic.rb b/activerecord/lib/active_record/locking/pessimistic.rb
index 66994e4797..58af92f0b1 100644
--- a/activerecord/lib/active_record/locking/pessimistic.rb
+++ b/activerecord/lib/active_record/locking/pessimistic.rb
@@ -38,6 +38,18 @@ module ActiveRecord
     #     account2.save!
     #   end
     #
+    # You can start a transaction and acquire the lock in one go by calling
+    # <tt>with_lock</tt> with a block. The block is called from within
+    # a transaction, the object is already locked. Example:
+    #
+    #   account = Account.first
+    #   account.with_lock do
+    #     # This block is called within a transaction,
+    #     # account is already locked.
+    #     account.balance -= 100
+    #     account.save!
+    #   end
+    #
     # Database-specific information on row locking:
     #   MySQL: http://dev.mysql.com/doc/refman/5.1/en/innodb-locking-reads.html
     #   PostgreSQL: http://www.postgresql.org/docs/current/interactive/sql-select.html#SQL-FOR-UPDATE-SHARE
@@ -50,6 +62,16 @@ module ActiveRecord
         reload(:lock => lock) if persisted?
         self
       end
+
+      # Wraps the passed block in a transaction, locking the object
+      # before yielding. You pass can the SQL locking clause
+      # as argument (see <tt>lock!</tt>).
+      def with_lock(lock = true)
+        transaction do
+          lock!(lock)
+          yield
+        end
+      end
     end
   end
 end