allow the 'lock_version' column to be configured with set_locking_column. Closes #3402

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3422 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 25 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/locking.rb b/activerecord/lib/active_record/locking.rb
index 71a4666e17..28d55da6df 100644
--- a/activerecord/lib/active_record/locking.rb
+++ b/activerecord/lib/active_record/locking.rb
@@ -18,6 +18,8 @@ module ActiveRecord
   # 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>
   module Locking
     def self.append_features(base) #:nodoc:
       super
@@ -29,13 +31,15 @@ module ActiveRecord
 
     def update_with_lock #:nodoc:
       if locking_enabled?
-        previous_value    = self.lock_version
-        self.lock_version = previous_value + 1
+        lock_col = self.class.locking_column
+        previous_value = send(lock_col)
+        send(lock_col + '=', previous_value + 1)
         
         affected_rows = connection.update(<<-end_sql, "#{self.class.name} Update with optimistic locking")
           UPDATE #{self.class.table_name}
           SET #{quoted_comma_pair_list(connection, attributes_with_quotes(false))}
-          WHERE #{self.class.primary_key} = #{quote(id)} AND lock_version = #{quote(previous_value)}
+          WHERE #{self.class.primary_key} = #{quote(id)} 
+          AND #{lock_col} = #{quote(previous_value)}
         end_sql
 
         unless affected_rows == 1
@@ -52,7 +56,24 @@ module ActiveRecord
     cattr_accessor :lock_optimistically
 
     def locking_enabled? #:nodoc:
-      lock_optimistically && respond_to?(:lock_version)
+      lock_optimistically && respond_to?(self.class.locking_column)
     end
+    
+    class << self
+      def set_locking_column( value=nil, &block )
+          define_attr_method :locking_column, value, &block
+      end
+  
+      def locking_column
+        reset_locking_column
+      end
+  
+      def reset_locking_column
+        default = 'lock_version'
+        set_locking_column(default)
+        default
+      end
+    end
+    
   end
 end