Migrations are always defined from one version to the other. When crossing several versions upon migration, several migrations should be combined. Or when migrating partially migrated databases, remaining migrations should be applied, not all. The rails approach may be suitable here. Furthermore, the user may want to compare a composed migration (from steps he wrote earlier) with a detected migration. Also, a composed transformation may provide options for simplification.

Submitted by Sander Vermolen on 12 August 2010 at 16:25