基本说明
用alembic --help命令查看使用说明
(py38-fastapi) ➜ 面向 alembic --help
usage: alembic [-h] [--version] [-c CONFIG] [-n NAME] [-x X] [--raiseerr]
{branches,current,downgrade,edit,ensure_version,heads,history,init,list_templates,merge,revision,show,stamp,upgrade}
...
positional arguments:
{branches,current,downgrade,edit,ensure_version,heads,history,init,list_templates,merge,revision,show,stamp,upgrade}
branches Show current branch points.
current Display the current revision for a database.
downgrade Revert to a previous version.
edit Edit revision script(s) using $EDITOR.
ensure_version Create the alembic version table if it doesn't exist already .
heads Show current available heads in the script directory.
history List changeset scripts in chronological order.
init Initialize a new scripts directory.
list_templates List available templates.
merge Merge two revisions together. Creates a new migration file.
revision Create a new revision file.
show Show the revision(s) denoted by the given symbol.
stamp 'stamp' the revision table with the given revision; don't run any
migrations.
upgrade Upgrade to a later version.
optional arguments:
-h, --help show this help message and exit
--version show program's version number and exit
-c CONFIG, --config CONFIG
Alternate config file; defaults to value of ALEMBIC_CONFIG environment
variable, or "alembic.ini"
-n NAME, --name NAME Name of section in .ini file to use for Alembic config
-x X Additional arguments consumed by custom env.py scripts, e.g. -x
setting1=somesetting -x setting2=somesetting
--raiseerr Raise a full stack trace on error
看着与git比较类似，有init merge不用的是有upgrade
-c命令，指自定义ini文件的名字
因此若生成指定的ini文件，及使用指定的ini文件进行迁移，需要使用如下命令：
# 初始化
alembic -c test1.ini init test1
# 提交更改
alembic -c test1.ini revision --autogenerate -m "height commit"
# 执行更改
alembic -c test1.ini upgrade head
更详细的执行可查看SQLAlchemy + alembic版本迁移数据库 - (jianshu.com)
若需要不同的迁移目录对应不同的数据库，需要对数据库的Base进行分割
拆分Base
说是拆分Base，其实是将建表的类继承自不同的对象基类
# models/base.py
from sqlalchemy.ext.declarative import declarative_base
# 创建对象基类
Base1 = declarative_base()
Base2 = declarative_base()
创建表时继承对应的基类即可
举例：User表
# models/user/models.py
from sqlalchemy import Column, String
from models.base import Base2 as Base
class User(Base):
"""
用户表
"""
__tablename__ = "users"
__table_args__ = {"comment": "用户表"}
user_id = Column(String(80), primary_key=True, unique=True, comment="用户id")
username = Column(String(30), nullable=False, unique=True, comment="登陆用户名")
create_time = Column(String(20), default="", comment="创建时间")
def __repr__(self):
return f""
Product表：
# models/product/models.py
from sqlalchemy import Column, Integer, String
from models.base import Base1 as Base
class ProductInfo(Base):
"""
用户表
"""
__tablename__ = "product_info"
__table_args__ = {"comment": "项目表"}
product_id = Column(Integer, primary_key=True,
autoincrement=True, comment="项目id")
user_id = Column(String(80), index=True, comment="创建项目用户id")
product_name = Column(String(30), nullable=False,
unique=True, comment="项目名")
create_time = Column(String(20), default="", comment="创建时间")
def __repr__(self):
return (
f""
)
以下解决方案来自 alembic + sqlalchemy 多个数据库答案 - 爱码网 (likecs.com)
Alembic 提供了一个模板来处理多个数据库：
alembic init --template multidb ./multidb
- 修改ini
#alembic.ini
databases = engine1, engine2
[engine1]
sqlalchemy.url = driver://user:pass@localhost/dbname
[engine2]
sqlalchemy.url = driver://user:pass@localhost/dbname2
- 将
multidb/env.py中的target_metadata指向对应模型【有更改】
# multidb/env.py
# 添加以下代码
import os
import sys
# 把当前项目路径加入到path中
sys.path.append(os.path.dirname(os.path.dirname(__file__)))
from models.base import Base1
from models.base import Base2
target_metadata = {
'engine1':Base1.metadata,
'engine2':Base2.metadata
}
- 测试Alembic设置
alembic revision --autogenerate -m "test"
- 使用Alembic迁移
alembic revision --autogenerate -m "one more db"
alembic upgrade head
其它模式
也可以基于不同的base生成不同的迁移目录，做到脚本配置与数据库一一对应。当下我没有此需求，故未做探究