alembic.ini

# A generic, single database configuration.
[application]
config_file_name = app_conf.py

[alembic]
# path to migration scripts
script_location = foo.bar:migrations

# template used to generate migration files
# file_template = %%(rev)s_%%(slug)s

# set to 'true' to run the environment during
# the 'revision' command, regardless of autogenerate
# revision_environment = false

# Logging configuration
[loggers]
keys = root,sqlalchemy,alembic

[handlers]
keys = console

[formatters]
keys = generic

[logger_root]
level = WARN
handlers = console
qualname =

[logger_sqlalchemy]
level = WARN
handlers =
qualname = sqlalchemy.engine

[logger_alembic]
level = INFO
handlers =
qualname = alembic

[handler_console]
class = StreamHandler
args = (sys.stderr,)
level = NOTSET
formatter = generic

[formatter_generic]
format = %(levelname)-5.5s [%(name)s] %(message)s
datefmt = %H:%M:%S

env.py

from __future__ import with_statement
import os.path
from alembic import context
from sqlalchemy import engine_from_config, pool
from logging.config import fileConfig

from foo.bar.database import db
from foo.bar.core import create_app

# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config

app = create_app(config.get_section_option('application', 'config_file_name'))
config.set_main_option('sqlalchemy.url', app.config['SQLALCHEMY_DATABASE_URI'])

# Interpret the config file for Python logging.
# This line sets up loggers basically.
fileConfig(config.config_file_name)

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
# target_metadata = None
target_metadata = db.metadata

# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.


def run_migrations_offline():
    """Run migrations in 'offline' mode.

    This configures the context with just a URL
    and not an Engine, though an Engine is acceptable
    here as well.  By skipping the Engine creation
    we don't even need a DBAPI to be available.

    Calls to context.execute() here emit the given string to the
    script output.

    """
    url = config.get_main_option("sqlalchemy.url")
    context.configure(url=url)

    with context.begin_transaction():
        context.run_migrations()


def run_migrations_online():
    """Run migrations in 'online' mode.

    In this scenario we need to create an Engine
    and associate a connection with the context.

    """
    engine = engine_from_config(
                config.get_section(config.config_ini_section),
                prefix='sqlalchemy.',
                poolclass=pool.NullPool)

    connection = engine.connect()
    context.configure(
                connection=connection,
                target_metadata=target_metadata
                )

    try:
        with context.begin_transaction():
            context.run_migrations()
    finally:
        connection.close()

if context.is_offline_mode():
    run_migrations_offline()
else:
    run_migrations_online()