Introducing Migrations to CodeIgniter

[eluser]sophistry[/eluser]
this looks really helpful. i've never used a db migration utility before but i've recently moved to a new version of a project and basically rewrote the entire schema by hand. but, after i'd done it i realized i had to get the existing data into the new schema. i normalized the schema and there was no easy way to rebuild it, so i did it piecemeal (coding custom importing loops by hand).

what do you do about the data when you remove or significantly alter a table? (e.g., normalize it)

is there a facility for backing up the data in the tables before migrations? restoring after? specifying alterations that result in normalization so the data can be cleanly moved just like the schema?

thanks!