Reset Alembic after deleting migration folder

Question

I accidentally deleted my migrations folder. So I ran flask db init, and everything ran smoothly. But when I ran flask db migrate, it gave me this error:

INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
ERROR [root] Error: Can't locate revision identified by '470572fac7a1'

From what I understand, it's looking for my other migration folder which is long gone. How can I solve this?

Answer 1

Delete that particular record in the table alembic_version that's in your database. There's only one varchar column called version_num, so this expression should work:

delete from alembic_version where version_num='470572fac7a1';

Answer 2

Delete the /migrations directory and rename/replicate your applications database. Then start from scratch.

flask db init
flask db migrate
flask db upgrade

Now repopulate your new empty database with data from your backup.