alembic 数据库管理工具的使用
安装方式:
- com进行安装
pip install alembic -i 国内源地址
- 编辑器安装
在设置里面找到三方库的安装目录,然后搜索alembic,点击安装
生成管理仓库:
在项目目录中输入
alembic init alembic
项目目录中会自动生成 alembic 版本管理文件夹以及 alembic.ini 的配置文件
创建模型:
在创建模型的时候需要构建一个数据表的基类
eg:
# Copyright (c) 2020—2021 Toplinker Corporation. All rights reserved. """ 数据表基类 """ from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.ext.declarative.api import DeclarativeMeta from app.core.settings import settings class PrefixMeta(DeclarativeMeta): """ 为表名添加前缀 """ def __init__(cls, classname, bases, dict_, **kw): if '__tablename__' in dict_: cls.__tablename__ = dict_['__tablename__'] = \ settings.table_prefix + dict_['__tablename__'] return super().__init__(classname, bases, dict_, **kw) # 数据表基类 Base = declarative_base(metaclass=PrefixMeta)
然后创建的模型的时候需要导入上面创建的基类
eg:
# Copyright (c) 2020—2021 Toplinker Corporation. All rights reserved. """ 用户表 """ from sqlalchemy import Column, Integer, String, Boolean, Text from app.models import Base class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, index=True) name = Column(String(255), unique=True, index=True, nullable=False) fullname = Column(String(255)) email = Column(String(255)) password = Column(String(512), nullable=False) is_active = Column(Boolean(), default=True) token_policy = Column(Integer, default=0) roles = Column(Text) remark = Column(Text)
修改alembic配置:
修改版本管理里面的env.py
将‘target_metadata = None’ 改为上面的基类,
修改alembic.ini文件
注释掉:
prepend_sys_path = . version_path_separator = os # default: use os.pathsep
更换sqlalchemy.url
postgresql+psycopg2://数据库用户:数据库密码@数据库IP地址:端口/数据库名称
生成迁移文件
alembic revision --autogenerate -m "message"
异常:
Traceback (most recent call last): File "G:\python_V\python3.8\lib\runpy.py", line 194, in _run_module_as_main return _run_code(code, main_globals, None, File "G:\python_V\python3.8\lib\runpy.py", line 87, in _run_code exec(code, run_globals) File "G:\python_object\object_fastapi\venv\Scripts\alembic.exe\__main__.py", line 7, in <module> File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\config.py", line 588, in main CommandLine(prog=prog).main(argv=argv) File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\config.py", line 582, in main self.run_cmd(cfg, options) File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\config.py", line 559, in run_cmd fn( File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\command.py", line 227, in revision script_directory.run_env() File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\script\base.py", line 563, in run_env util.load_python_file(self.dir, "env.py") File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\util\pyfiles.py", line 92, in load_python_file module = load_module_py(module_id, path) File "g:\python_object\object_fastapi\venv\lib\site-packages\alembic\util\pyfiles.py", line 108, in load_module_py spec.loader.exec_module(module) # type: ignore File "<frozen importlib._bootstrap_external>", line 848, in exec_module File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed File "G:\python_object\object_fastapi\backend\alembic\env.py", line 20, in <module> from app.models.base import Base ModuleNotFoundError: No module named 'app.models.base'
原因: 没有找到对应的文件地方
解决方式:将目录临时加入环境变量种
import os
import sys; sys.path.append(os.getcwd())
然后再执行生成迁移文件命令:成功
alembic模块案例:
env.py:
from logging.config import fileConfig from sqlalchemy import engine_from_config from sqlalchemy import pool from alembic import context import os import sys; sys.path.append(os.getcwd()) # 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 from app.models.base import Base target_metadata = Base.metadata # target_metadata = None # 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()
alembic.ini:
# A generic, single database configuration. [alembic] # path to migration scripts script_location = alembic # template used to generate migration files # file_template = %%(rev)s_%%(slug)s # sys.path path, will be prepended to sys.path if present. # defaults to the current working directory. ;prepend_sys_path = . # timezone to use when rendering the date within the migration file # as well as the filename. # If specified, requires the python-dateutil library that can be # installed by adding `alembic[tz]` to the pip requirements # string value is passed to dateutil.tz.gettz() # leave blank for localtime # timezone = # max length of characters to apply to the # "slug" field # truncate_slug_length = 40 # set to 'true' to run the environment during # the 'revision' command, regardless of autogenerate # revision_environment = false # set to 'true' to allow .pyc and .pyo files without # a source .py file to be detected as revisions in the # versions/ directory # sourceless = false # version location specification; This defaults # to alembic/versions. When using multiple version # directories, initial revisions must be specified with --version-path. # The path separator used here should be the separator specified by "version_path_separator" # version_locations = %(here)s/bar:%(here)s/bat:alembic/versions # version path separator; As mentioned above, this is the character used to split # version_locations. Valid values are: # # version_path_separator = : # version_path_separator = ; # version_path_separator = space ;version_path_separator = os # default: use os.pathsep # the output encoding used when revision files # are written from script.py.mako # output_encoding = utf-8 ;sqlalchemy.url = driver://user:pass@localhost/dbname sqlalchemy.url = postgresql+psycopg2://账号:密码@127.0.0.1:5432/数据库名 [post_write_hooks] # post_write_hooks defines scripts or Python functions that are run # on newly generated revision scripts. See the documentation for further # detail and examples # format using "black" - use the console_scripts runner, against the "black" entrypoint # hooks = black # black.type = console_scripts # black.entrypoint = black # black.options = -l 79 REVISION_SCRIPT_FILENAME # 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
更新数据库:
将迁移文件推送收到数据库:alembic upgrade head
回滚版本(将head指向上一版本,然后再推到数据库):alembic downgrade head
成功,
注:此处需要先创建一个配置中的数据库
更新模型代码之后更新数据库:
执行代码
更新迁移文件:alembic revision --autogenerate -m "message"
更新到数据库:alembic upgrade head
命令参数:
init:创建一个alembic仓库。 revision:创建一个新的版本文件。 --autogenerate:自动将当前模型的修改,生成迁移脚本。 -m:本次迁移做了哪些修改,用户可以指定这个参数,方便回顾。 upgrade:将指定版本的迁移文件映射到数据库中,会执行版本文件中的upgrade函数。如果有多个迁移脚本没有被映射到数据库中,那么会执行多个迁移脚本。 [head]:代表最新的迁移脚本的版本号。 downgrade:会执行指定版本的迁移文件中的downgrade函数。 heads:展示head指向的脚本文件版本号。 history:列出所有的迁移版本及其信息。 current:展示当前数据库中的版本号
推送异常
1、 FAILED: Target databases is not up to data
原因:head与current不同步了,current落后于head
解决方式: 将current移动到head上面,让他们同步: alembic upgrade head
2、 FAILED:Can`t locate servision identified by '2576567567'
原因:数据库种存的版本号不在迁移文件目录中
解决方式:删除数据库里面的版本号(即alembic_version表中的数据),然后在执行 :alembic upgrade head