CommandError: Can't locate revision identified by '...' when migrating using Flask-Migrate

Question

I started using Flask-Migrate today and installed it on a test project. However i am getting following error:

alembic.util.exc.CommandError: Can't locate revision identified by 'e39d16e62810'

Steps to reproduce:

1. run "python create_db.py"
2. run "flask db init"
3. add column "name" to Entry-model
4. run "flask db migrate"

EDIT: After removing migrations directory and repeating the process i am getting the same error after running "flask db migrate". I also tried using a manage.py file with flask-script --> same issue

Error:

(venv_mentz) H:\Flask-API-Test>python manage.py db migrate INFO  [alembic.runtime.migration] Context impl SQLiteImpl. INFO  [alembic.runtime.migration] Will assume non-transactional DDL. Traceback (most recent call last):   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 143, in _catch_revision_errors     yield   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 206, in get_revisions     return self.revision_map.get_revisions(id_)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 299, in get_revisions     return sum([self.get_revisions(id_elem) for id_elem in id_], ())   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 299, in <listcomp>     return sum([self.get_revisions(id_elem) for id_elem in id_], ())   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 304, in get_revisions     for rev_id in resolved_id)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 304, in <genexpr>     for rev_id in resolved_id)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 362, in _revision_for_ident     resolved_id) alembic.script.revision.ResolutionError: No such revision or branch 'e39d16e62810'  The above exception was the direct cause of the following exception:  Traceback (most recent call last):   File "manage.py", line 14, in <module>     manager.run()   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\flask_script\__init__.py", line 417, in run     result = self.handle(argv[0], argv[1:])   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\flask_script\__init__.py", line 386, in handle     res = handle(*args, **config)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\flask_script\commands.py", line 216, in __call__     return self.run(*args, **kwargs)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\flask_migrate\__init__.py", line 197, in migrate     version_path=version_path, rev_id=rev_id)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\command.py", line 176, in revision     script_directory.run_env()   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 425, in run_env     util.load_python_file(self.dir, 'env.py')   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\util\pyfiles.py", line 81, in load_python_file     module = load_module_py(module_id, path)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\util\compat.py", line 83, in load_module_py     spec.loader.exec_module(module)   File "<frozen importlib._bootstrap_external>", line 678, in exec_module   File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed   File "migrations\env.py", line 87, in <module>     run_migrations_online()   File "migrations\env.py", line 80, in run_migrations_online     context.run_migrations()   File "<string>", line 8, in run_migrations   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\runtime\environment.py", line 836, in run_migrations     self.get_context().run_migrations(**kw)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\runtime\migration.py", line 321, in run_migrations     for step in self._migrations_fn(heads, self):   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\command.py", line 156, in retrieve_migrations     revision_context.run_autogenerate(rev, context)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\autogenerate\api.py", line 415, in run_autogenerate     self._run_environment(rev, migration_context, True)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\autogenerate\api.py", line 425, in _run_environment     if set(self.script_directory.get_revisions(rev)) != \   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 206, in get_revisions     return self.revision_map.get_revisions(id_)   File "c:\users\marschall\appdata\local\programs\python\python36-32\Lib\contextlib.py", line 100, in __exit__     self.gen.throw(type, value, traceback)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 174, in _catch_revision_errors     compat.raise_from_cause(util.CommandError(resolution))   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\util\compat.py", line 194, in raise_from_cause     reraise(type(exception), exception, tb=exc_tb, cause=exc_value)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\util\compat.py", line 187, in reraise     raise value.with_traceback(tb)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 143, in _catch_revision_errors     yield   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\base.py", line 206, in get_revisions     return self.revision_map.get_revisions(id_)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 299, in get_revisions     return sum([self.get_revisions(id_elem) for id_elem in id_], ())   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 299, in <listcomp>     return sum([self.get_revisions(id_elem) for id_elem in id_], ())   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 304, in get_revisions     for rev_id in resolved_id)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 304, in <genexpr>     for rev_id in resolved_id)   File "H:\Flask-API-Test\venv_mentz\lib\site-packages\alembic\script\revision.py", line 362, in _revision_for_ident     resolved_id) alembic.util.exc.CommandError: Can't locate revision identified by 'e39d16e62810' 

My file structure looks like this:

app -- views ----- __init__.py ----- main.py -- __init__.py -- config.py -- models.py instance -- __init__.py -- config.py create_db.py dev.db run.py 

My app factory:

from flask import Flask from instance.config import app_config from flask_migrate import Migrate  def create_app(config_name):     """ Creates a runnable app.         This app will be using the config with name "config_name".     """     app = Flask(__name__)     # Loading the the config from instance folder with name "config_name"     app.config.from_object(app_config[config_name])     # Loading generic config from 'config.py'     app.config.from_pyfile('config.py')      # Registering this app at db     from app.models import db     db.init_app(app)     migrate = Migrate(app, db)      from app import models, views      return app 

My run.py:

""" This script runs a the app with the given configuration. """  from app import create_app  # Configuration used to run the app config_name = 'dev'  # Creating the app by using the required configuration app = create_app(config_name)  if __name__ == '__main__':     app.run() 

And my create_db.py file to create the database using models.py:

""" This script creates the database defined in app.models. """  from app import create_app  app = create_app('dev') from app.models import db  # Telling SQLAlchemy what app should be used as the database model with app.app_context():     db.create_all() 

This is my models.py:

from flask_sqlalchemy import SQLAlchemy  db = SQLAlchemy()  class Entry(db.Model):     __tablename__ = 'Entries'     layer_id = db.Column(db.Integer, primary_key=True)      def __repr__(self):         return "ID: {}; text: {}".format(self.layer_id, self.text) 

EDIT: manage.py:

from flask_script import Manager from flask_migrate import Migrate, MigrateCommand from app import create_app from app import models from app.models import db  app = create_app('dev') migrate = Migrate(app, db) manager = Manager(app)  manager.add_command('db', MigrateCommand)  if __name__ == '__main__':     manager.run() 

Answer 1

you delete the migration directory but the version has been saved in the database, so you have to delete the version info in the dabase, run

delete from alembic_version;

in mysql shell.

As suggested by @mirekphd, If this is a developing environment or a single app for test, just delete it, Else BACKUP the data in the table.

Answer 2

In my case I have accidentally deleted the most recent migration file but the alembic version (alembic_version) table refers to the deleted version.

So instead of droping the entire database, you can change the version_num field in the alembic_version table.

Following steps worked for me:

• Find the head using db history
• Update the version_num field to the head version.
• run migrate using db migrate
• upgrade the database db upgrade