Я следовал документации от Alembic для автоматического создания миграции. Структура моего проекта выглядит так:
alembic/
versions/
env.py
README
script.py.mako
data/
__init__.py
db.py
models.py
alembic.ini
app.db
Я внес изменения в env.py, точно следуя документу:
from logging.config import fileConfig
from sqlalchemy import engine_from_config
from sqlalchemy import pool
from alembic import context
from data.models import Base
# 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 = Base.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,
target_metadata=target_metadata,
literal_binds=True,
dialect_opts={"paramstyle": "named"},
)
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(
config.get_section(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()
Это мой __init__.py:
import os
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from .models import Base
basedir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
db_url = os.environ.get('DATABASE_URL') or \
'sqlite:///' + os.path.join(basedir, 'app.db')
engine = create_engine(db_url, echo=False)
Base.metadata.create_all(engine)
session = sessionmaker(bind=engine)
Я создал класс пользователя в models.py следующим образом:
from sqlalchemy import Column, Sequence, Integer, String
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class User(Base):
__tablename__ = 'user'
id = Column(Integer, Sequence('id_seq'), primary_key=True)
first_name = Column(String, nullable=False)
last_name = Column(String, nullable=False)
def __repr__(self):
return "<%s('%s', '%s')>" \
% (self.__class__.__qualname__, self.first_name,
self.last_name)
После этого я запускаю миграцию:
alembic revision --autogenerate -m "Added user table"
Однако я получил пустые обновления() и понижение() в файле миграции:
"""Added user table
Revision ID: 279933caec54
Revises:
Create Date: 2021-05-12 16:21:05.772568
"""
from alembic import op
import sqlalchemy as sa
# revision identifiers, used by Alembic.
revision = '279933caec54'
down_revision = None
branch_labels = None
depends_on = None
def upgrade():
# ### commands auto generated by Alembic - please adjust! ###
pass
# ### end Alembic commands ###
def downgrade():
# ### commands auto generated by Alembic - please adjust! ###
pass
# ### end Alembic commands ###
Но когда я проверил базу данных, там была создана пользовательская таблица (сам я этого не делал). Как это случилось? Как alembic создал пустую миграцию, но создал таблицу?
