SQLAlchemy Alembic

1. 安装：pip install alembic
2. 初始化alembic:

   (venv) F:CodeAllProjectdevInfomodels>alembic init alembic
   Creating directory F:CodeAllProjectdevInfomodelsalembic ... done
    Creating directory F:CodeAllProjectdevInfomodelsalembicversions ... done
    Generating F:CodeAllProjectdevInfomodelsalembic.ini ... done
    Generating F:CodeAllProjectdevInfomodelsalembicenv.py ... done
    Generating F:CodeAllProjectdevInfomodelsalembicREADME ... done
    Generating F:CodeAllProjectdevInfomodelsalembicscript.py.mako ... done
    Please edit configuration/connection/logging settings in 'F:\Code\AllProject\devInfo\models\alembic.ini' before proceeding.

3. 修改配置
• 修改文件(alembic.ini)：

定义sqlalchemy.url，写法和sqlalchemy中定义engine一样

sqlalchemy.url = mysql://root:123.com@127.0.0.1/allproject

• 修改alembic/env.py文件，修改metadata定义

# target_metadata = None
import os,sys
sys.path.append(os.path.realpath('.'))
from baseobj import Base
target_metadata=Base.metadata

4. 数据库结构修改
5. 生成版本文件，在alembic下的version下面生成一个文件，版本号_描述

(venv) F:models>alembic revision --autogenerate -m "test update db"
INFO  [alembic.runtime.migration] Context impl MySQLImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.autogenerate.compare] Detected removed table 'mib'
INFO  [alembic.autogenerate.compare] Detected removed table 'device'
INFO  [alembic.autogenerate.compare] Detected removed table 'board'
INFO  [alembic.autogenerate.compare] Detected removed table 'ips'
Generating F:modelsalembicversions45c578f737cc_test_update_db.py ... done

6. 升级数据库：head表示最新版本文件，也可以直接指定版本号

   (venv) F:models>alembic upgrade head
   INFO  [alembic.runtime.migration] Context impl MySQLImpl.
   INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
   INFO  [alembic.runtime.migration] Running upgrade  -> 45c578f737cc, test update db

7. 降级数据库，alembic downgrade xxxx-1,-1表示上一个版本

(venv) F:models>alembic downgrade 45c578f737cc-1
INFO  [alembic.runtime.migration] Context impl MySQLImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.runtime.migration] Running downgrade 45c578f737cc -> , test update db

8. 手动编辑版本文件

   def upgrade():
       # ### commands auto generated by Alembic - please adjust! ###
       #添加行，board为表名，test_column为新加字段
       op.add_column('board',sa.Column('test_column',sa.Integer))
       
   def downgrade():
       #降级删除指定表指定列
       op.drop_column('board','test_column')