Cannot complete Flask-Migration

flask-migrate will create a table named "alembic_version" in your database.
so you should drop this table and delete migrations folder in your project.
and then use $ python app.py db init again...
I think $ python app.py db migrate will work fine.

Alembic keeps the migration history in your database, this is why it still recognises there is another revision there. I keep my project on Heroku so I was able to just do heroku pg:pull ... to be able to get a new copy of my database. Prior to this you will have to drop your local db. In case you don't want to drop your local, I think dropping the table should work too. I use the PG Commander as a GUI tool to quickly browse my databases.

the first step to do is run this command alembic currentyou should get an error as mentioned above (the goal is to make sure that this command returns a valid response).

the reason why u're getting this is bc alembic is confused about your current state.. it's assuming that you should be in revision 39408d6b248d but then decides that that revision is invalid.

to investigate this, let's find out which revisions are considered valid by alembic, run this command:

alembic history --verbose

you'll get a list of all previous revisions (note: it's a good idea to attach a message beside each revision.. think about it as a good git commit message)

Rev: 594cc72f56fd (head)Parent: 262f40e28682Path: ***************    adjust context_id in log table so that it is a substring of the object_id    Revision ID: 594cc72f56fd    Revises: 262f40e28682    Create Date: 2015-07-22 14:31:52.424862Rev: 262f40e28682Parent: 1dc902bd1c2Path: ***************    add context_id column to log table    Revision ID: 262f40e28682    Revises: 1dc902bd1c2    Create Date: 2015-07-22 11:05:37.654553Rev: 1dc902bd1c2Parent: <base>Path: ***************    Initial database setup    Revision ID: 1dc902bd1c2    Revises:     Create Date: 2015-07-06 09:55:11.439330

the revision 39408d6b248d clearly doesn't exist in the above revisions. This revision is stored in the alembic_table in the database.. you can verify by going to your dbase and running:

$ select * from alembic_version; version_num  -------------- 57ac999dcaa7

so now you should review the state of your database and see where it fits vis-a-vis the revisions outputted above:

in my case, by poking around my dbase it becomes obvious which revision i'm in right now.. which is that dbase has been setup,, but the other revisions haven't been included yet.

so now i replace the value on the dbase with the one i found from the history command above:

vibereel=> update alembic_version set version_num = '1dc902bd1c2';

and now running alembic current returns

INFO  [alembic.migration] Context impl PostgresqlImpl.INFO  [alembic.migration] Will assume transactional DDL.1dc902bd1c2

done.