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迁移

数据库初始化

请注意，所有示例都假设您已经有一个数据库。

如果情况并非如此，并且您需要创建表，那么这非常简单，因为 ormar 使用 sqlalchemy 进行基础表构建。

您所要做的就是像下面的示例一样调用 create_all() 。

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import sqlalchemy
# get your database url in sqlalchemy format - same as used with databases instance used in Model definition
engine = sqlalchemy.create_engine("sqlite:///test.db")
# note that this has to be the same metadata that is used in ormar Models definition
metadata.create_all(engine)

您还可以创建单个表，sqlalchemy 表在 ormar.ormar_config 对象中公开。

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import sqlalchemy
# get your database url in sqlalchemy format - same as used with databases instance used in Model definition
engine = sqlalchemy.create_engine("sqlite:///test.db")
# Artist is an ormar model from previous examples
Artist.ormar_config.table.create(engine)

!!!警告您只需创建表一次，因此请使用 python 控制台，或者在首次使用后从生产代码中删除脚本。

蒸馏器的用法

与表一样，由于我们将表基于 sqlalchemy 进行迁移，因此请使用 alembic。

初始化

使用命令行重现这个简约的示例。

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alembic init alembic
alembic revision --autogenerate -m "made some changes"
alembic upgrade head

示例 env.py 文件

蒸馏器迁移的一个简单示例应该类似于：

当您的应用程序结构如下：

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-> app
    -> alembic (initialized folder - so run alembic init alembic inside app folder)
    -> models (here are the models)
      -> __init__.py
      -> my_models.py

您的 env.py 文件（在 alembic 文件夹中）可能类似于：

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from logging.config import fileConfig
from sqlalchemy import create_engine

from alembic import context
import sys, os

# add app folder to system path (alternative is running it from parent folder with python -m ...)
myPath = os.path.dirname(os.path.abspath(__file__))
sys.path.insert(0, myPath + '/../../')

# 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 (the one used in ormar)
# for 'autogenerate' support
from app.models.my_models import metadata
target_metadata = metadata


# set your url here or import from settings
# note that by default url is in saved sqlachemy.url variable in alembic.ini file
URL = "sqlite:///test.db"


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.

    """
    context.configure(
        url=URL,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
        # if you use UUID field set also this param
        # the prefix has to match sqlalchemy import name in alembic
        # that can be set by sqlalchemy_module_prefix option (default 'sa.')
        user_module_prefix='sa.'
    )

    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 = create_engine(URL)

    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=target_metadata,
            # if you use UUID field set also this param
            # the prefix has to match sqlalchemy import name in alembic
            # that can be set by sqlalchemy_module_prefix option (default 'sa.')
            user_module_prefix='sa.'
        )

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


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

排除表格

您还可以使用传递给 context.configure 的 include_object 参数来包含/排除特定表。这应该是一个为给定对象返回 True/False 的函数。

示例函数排除名称中以 data_ 开头的表，除非它是“data_jobs”：

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def include_object(object, name, type_, reflected, compare_to):
    if name and name.startswith('data_') and name not in ['data_jobs']:
        return False

    return True

!!!注意 include_objects 的函数参数（您可以更改名称）是必需的，并在 alembic 中定义，以检查它们的作用，请检查 alembic 文档

然后将其传递到上下文中（在线和离线）：

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context.configure(
        url=URL,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
        user_module_prefix='sa.',
        include_object=include_object
    )

!!!info 您可以在 sqlalchemy 表创建文档中阅读有关表创建、更改和迁移的更多信息。