brewster/shearwater — pull request #1 by cyphactor (2012-11-29 09:35:22+00:00)
Title: Handle range ghosts in cql backend

I did this because when you have your Cassandra schema_migrations column
family setup as follows you end up still getting "range ghosts". This was
breaking the last_migration method in such a way that I was always getting a
migration that I had previously rollback and was now a "range ghost" as the
last_migration result.

```CREATE COLUMNFAMILY schema_migrations (version int PRIMARY KEY, migrated_at timestamp)```

As a side effect of this it was causing Migrator rollback method to all keep trying to rollback the migration it just rolled back.