title: NHibernate SchemaUpdate still wants to recreate table
body: <p>I am using NHibernate with Fluent on my SQL Server 2012 and I've decided to use SchemaUpdater instead of SchemaExport becouse I dont want my data to disappear. I've created method like this:</p>
  
  <pre><code> public void UpdateSchema(Configuration config)
      {
          System.Action&lt;string&gt; updateExport = x =&gt;
          {
              using (var file = new System.IO.FileStream(@"C:\tmp\update.sql", System.IO.FileMode.Append, System.IO.FileAccess.Write))
              using (var sw = new System.IO.StreamWriter(file))
              {
                  sw.Write(x);
                  sw.Close();
              }
          };
          NHibernate.Tool.hbm2ddl.SchemaUpdate SchemaUpdater = new NHibernate.Tool.hbm2ddl.SchemaUpdate(config);
          SchemaUpdater.Execute(updateExport, true); 
  
      }
  </code></pre>
  
  <p>My database is creating but when i want to add new field to my model i get an error:<code>"Invalid column name 'xxx'.
  ↵Invalid column name 'xxx'."</code></p>
  
  <p>I've decided to debug and check SchemaUpdater.Exceptions, there was:</p>
  
  <pre><code>Count = 4
  [0]: {"There is already an object named 'User' in the database."}
  [1]: {"There is already an object named 'FK5E008E27F9F9FA61' in the database.\r\nCould not create constraint. See previous errors."}
  [2]: {"There is already an object named 'FK5E008E27194964AD' in the database.\r\nCould not create constraint. See previous errors."}
  [3]: {"There is already an object named 'FK5E008E27713F97F9' in the database.\r\nCould not create constraint. See previous errors."}
  </code></pre>
  
  <p>This looks like program wants still to create new table, not to update it, sql which is created and sent to db:</p>
  
  <pre><code>create table [User] (
      Id INT IDENTITY NOT NULL,
     Acount NVARCHAR(255) null,
     Email NVARCHAR(255) null,
     (...)
     xxx NVARCHAR(255) null,
     Manager_id INT null,
     Evaluator_id INT null,
     WorkTimeAdmin_Id INT null,
     primary key (Id)
  )
  alter table [User] 
      add constraint FK5E008E27F9F9FA61 
      foreign key (Manager_id) 
      references [User]
  alter table [User] 
      add constraint FK5E008E27194964AD 
      foreign key (Evaluator_id) 
      references [User]
  alter table [User] 
      add constraint FK5E008E27713F97F9 
      foreign key (WorkTimeAdmin_Id) 
      references [User]
  </code></pre>
  
  <p>I really want an automated solution, so no copying and editing sql's
  any ideas what should i change?</p>