artemis/core/data/alembic/env.py

from __future__ import with_statement

import asyncio
import threading
from logging.config import fileConfig

from alembic import context
from sqlalchemy import pool
from sqlalchemy.engine import Connection
from sqlalchemy.ext.asyncio import async_engine_from_config

from core.data.schema.base import metadata

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

# 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 = 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.

    """
    raise Exception("Not implemented or configured!")

    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 do_run_migrations(connection: Connection) -> None:
    context.configure(
        connection=connection,
        target_metadata=target_metadata,
        compare_type=True,
        compare_server_default=True,
    )

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


async def run_async_migrations() -> None:
    """In this scenario we need to create an Engine
    and associate a connection with the context.

    """
    ini_section = config.get_section(config.config_ini_section)
    overrides = context.get_x_argument(as_dictionary=True)
    for override in overrides:
        ini_section[override] = overrides[override]

    connectable = async_engine_from_config(
        ini_section, prefix="sqlalchemy.", poolclass=pool.NullPool
    )

    async with connectable.connect() as connection:
        await connection.run_sync(do_run_migrations)

    await connectable.dispose()


def run_migrations_online():
    try:
        loop = asyncio.get_running_loop()
    except RuntimeError:
        # there's no event loop
        asyncio.run(run_async_migrations())
    else:
        # there's currently an event loop and trying to wait for a coroutine
        # to finish without using `await` is pretty wormy. nested event loops
        # are explicitly forbidden by asyncio.
        #
        # take the easy way out, spawn it in another thread.
        thread = threading.Thread(target=asyncio.run, args=(run_async_migrations(),))
        thread.start()
        thread.join()


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