SqlAlchemy 迁移声明式答案

【问题标题】：SqlAlchemy Migrate DeclarativeSqlAlchemy 迁移声明式
【发布时间】：2011-10-10 19:16:06
【问题描述】：

我已将 SqlAlchemy-Migrate tutorial 上的教程修改为我的 Pylons Pyramid 项目的声明性语法。我可以成功升级和降级，但我担心下面的Base.metadata.drop_all(migrate_engine) 命令。这是我的迁移文件：

from sqlalchemy import Column
from sqlalchemy.types import Integer, String, DateTime
from sqlalchemy.sql import func
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker

from zope.sqlalchemy import ZopeTransactionExtension

DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    email = Column(String(75), unique=True)
    fullname = Column(String(60))          
    password = Column(String(51))          
    last_login = Column(DateTime)          
    date_joined = Column(DateTime, default=func.now())

def upgrade(migrate_engine):
    # Upgrade operations go here. Don't create your own engine; bind migrate_engine
    # to your metadata
    Base.metadata.bind = migrate_engine
    Base.metadata.create_all(migrate_engine) # IS THIS DANGEROUS?

def downgrade(migrate_engine):
    # Operations to reverse the above upgrade go here.
    Base.metadata.bind = migrate_engine
    Base.metadata.drop_all(migrate_engine) # IS THIS DANGEROUS?

[编辑] 我的问题是如何单独创建表格。我不知道这是我的问题，直到问了足够多的错误问题，才得到正确的问题。

【问题讨论】：

标签： python orm sqlalchemy pylons pyramid

【解决方案1】：

升级的正确解决方案是获取表并单独创建它，如下所示：

def upgrade(migrate_engine):
    # Upgrade operations go here. Don't create your own engine; bind migrate_engine
    # to your metadata
    User.__table__.create(migrate_engine)

并且，对于降级：

def downgrade(migrate_engine):
    # Operations to reverse the above upgrade go here.
    User.__table__.drop(migrate_engine)

【讨论】：