from Big Table's perspective there is no such thing as migrations. fields present when you write the record are stored, fields not present are not stored. so from that perspective the migrations work great!
some cautions: - when you remove fields, that data will not be removed from the datastore, you will need to iterate the records and remove the properties - if you want to assign a default value to a new property you will have to iterate the existing records and add the property with the default. aside from the deletion this is about the same as migrations on SQL backends. cfh
