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这是一个项目的一部分，该项目涉及使用 tg2 处理其中的 2 个数据库（该模型使用的是 mssql）。因为我需要读取/写入的表是使用不同的应用程序创建和管理的，所以我不希望 turbogears 覆盖/更改表 - 只需使用现有表 - 所以我使用 sqlalchemy 神奇的“自动加载”反射（我也不知道 mssql db 中这个表配置的每个细节model.__init__.py）由于 tg2 内部工作，一些反射是在课堂上而不是在课堂上完成的（正如一些 sqlalchemy 教程所建议的那样）

这是我收到的错误消息：（数据库中的表名是 SOMETABLE，在我的应用程序中，类是活动）

sqlalchemy.exc.ArgumentError: Mapper Mapper|Activities|SOMETABLE could not
 assemble any primary key columns for mapped table 'SOMETABLE'

这是活动课：

class Activities(DeclarativeBase2):

    __tablename__ = 'SOMETABLE'
    #tried the classic way, I used in another place without tg but didn't work here -      the reflection should be outside the class
    #__table_args__=  {'autoload':True
                      #,'autoload_with':engine2
                     #}
    def __init__(self,**kw):
        for k,v in kw.items():
            setattr(self,k,v)

这是model.__init__.py初始化模型方法（调用反射的地方）：

def init_model(engine1,engine2):
    """Call me before using any of the tables or classes in the model."""
    DBSession.configure(bind=engine1)
    DBSession2.configure(bind=engine2)

    # If you are using reflection to introspect your database and create
    # table objects for you, your tables must be defined and mapped inside
    # the init_model function, so that the engine is available if you
    # use the model outside tg2, you need to make sure this is called before
    # you use the model.

    #
    # See the following example:
    metadata.bind = engine1
    metadata2.bind = engine2
    #metadata2=MetaData(engine2)

    global t_reflected
    #
    t_reflected = Table("SOMETABLE", metadata2,
        autoload=True, autoload_with=engine2)
    #
    mapper(Activities, t_reflected

所以我想我需要告诉 sqlalchemy 什么是主键 - 但是在使用反射时我该怎么做（我知道主键字段）？

编辑工作解决方案：

def init_model(engine1,engine2):
    """Call me before using any of the tables or classes in the model."""
    DBSession.configure(bind=engine1)
    DBSession2.configure(bind=engine2)

    # If you are using reflection to introspect your database and create
    # table objects for you, your tables must be defined and mapped inside
    # the init_model function, so that the engine is available if you
    # use the model outside tg2, you need to make sure this is called before
    # you use the model.

    #
    # See the following example:
    metadata.bind = engine1
    metadata2.bind = engine2
    #metadata2=MetaData(engine2)

    global t_reflected
    #
    t_reflected = Table("SOMETABLE", metadata2,String,primary_key=True),
        autoload=True, autoload_with=engine2)# adding the primary key column here didn't work
    #
    mapper(Activities, t_reflected, non_primary=True)# notice the needed non_primary - for some reason I can't do the whole mapping in one file and I Have to do part in init_model and part in the model - quite annoying

同样在模型中，我必须添加主键列：

class Activities(DeclarativeBase2):

__tablename__ = 'SOMETABLE'
#tried the classic way, I used in another place without tg but didn't work here -      the reflection should be outside the class
EVENTCODE = Column(String, primary_key=True)# needed because the reflection couldn't find the primary key .

当然，我还必须添加各种导入model.__init__.py来完成这项工作

奇怪的是，它甚至在连接到数据库之前抱怨没有找到主键，并且当一个独立的 sqlalchemy 类（没有 tg2）执行相同的键时 - 根本没有抱怨。让你想知道

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1 回答 1

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您可以混合搭配：请参阅文档中的覆盖反射列。在您的情况下，代码看起来类似于：

t_reflected = Table("SOMETABLE", metadata2,
    Column('id', Integer, primary_key=True), # override reflected '???' column to have primary key
    autoload=True, autoload_with=engine2)

编辑1：模型版本：我也认为只有声明版本也可以工作，在这种情况下你不应该定义一个表t_reflected，也不应该手动映射那些，mapper(...)因为声明类是自动映射的：

class Activities(DeclarativeBase2):
    __table__ = Table('SOMETABLE', metadata2,
        Column('EVENTCODE', Unicode, primary_key=True),
        autoload=True, autoload_with=engine2,
    )
    def __init__(self,**kw):
        for k,v in kw.items():
            setattr(self,k,v)
于 2011-11-21T12:28:16.300 回答