ogn-python/alembic/env.py

import os
import importlib

from alembic import context
from sqlalchemy import engine_from_config, pool
from logging.config import fileConfig


# Provides access to the values within the .ini file in use.
alembic_config = context.config

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

# Get database path from ogn config
os.environ.setdefault('OGN_CONFIG_MODULE', 'config.default')
ogn_config = importlib.import_module(os.environ['OGN_CONFIG_MODULE'])

alembic_config.set_main_option('sqlalchemy.url', ogn_config.SQLALCHEMY_DATABASE_URI)

# Import metadata for autogeneration of migrations
from ogn.model import Base
target_metadata = Base.metadata


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, target_metadata=target_metadata, literal_binds=True)

    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.

    """
    connectable = engine_from_config(
        alembic_config.get_section(alembic_config.config_ini_section),
        prefix='sqlalchemy.',
        poolclass=pool.NullPool)

    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=target_metadata
        )

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

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