Implement a new remove_default_constraint method that uses sp_helpconstraint

Author: metaskills

CHANGELOG

@@ -1,6 +1,8 @@
 
 MASTER
 
+* Implement a new remove_default_constraint method that uses sp_helpconstraint [Ken Collins]
+
 * Use a lazy match in add_order_by_for_association_limiting! to allow sub selects to be used. Resolves 
   ticket #11.
 

lib/active_record/connection_adapters/sqlserver_adapter.rb

@@ -908,9 +908,10 @@ def remove_check_constraints(table_name, column_name)
       end
 
       def remove_default_constraint(table_name, column_name)
-        constraints = select_values("SELECT def.name FROM sysobjects def, syscolumns col, sysobjects tab WHERE col.cdefault = def.id AND col.name = '#{quote_string(column_name)}' AND tab.name = '#{quote_string(table_name)}' AND col.id = tab.id")
-        constraints.each do |constraint|
-          do_execute "ALTER TABLE #{quote_table_name(table_name)} DROP CONSTRAINT #{quote_column_name(constraint)}"
+        select_all("EXEC sp_helpconstraint '#{quote_string(table_name)}','nomsg'").select do |row|
+          row['constraint_type'] == "DEFAULT on column #{column_name}"
+        end.each do |row|
+          do_execute "ALTER TABLE #{quote_table_name(table_name)} DROP CONSTRAINT #{row['constraint_name']}"
         end
       end