How can I generate “migration” DDL from NHibernate mapping files?

Question

I'm using NHibernate 2 and PostgreSQL in my project. SchemaExport class does a great job generating DDL scheme for database, but it's great until the first application.

Is there any way to generate "migration" DLL (batch of "ALTER TABLE"'s instead of DROP/CREATE pair) using NHibernate mapping files?

Answer 1

Look into SchemaUpdate. Very similiar API as SchemaExport but it only creates migrations.

Answer 2

While SchemaUpdate very much answers my needs, it still has several problems. For example it refuses to put a new restriction on existing database column even if it's not gonna conflict with existing data.

I'm going froward to extend SchemaUpdate a little bit or, if fail, switch to one of that hand driven migration tools (for example Rails one).