Python 所有列上的SQLAlchemy继承筛选器
因此,我想对使用表继承的数据库模型的所有Python 所有列上的SQLAlchemy继承筛选器,python,inheritance,sqlalchemy,Python,Inheritance,Sqlalchemy,因此,我想对使用表继承的数据库模型的所有列执行一个过滤器。我无法确定这是否真的可以做到 首先,让我们使用同一个继承示例,该示例来自刚刚稍加修改的。我省略了这里的导入 class Employee(Base): __tablename__ = 'employee' id = Column(Integer, primary_key=True) name = Column(String(50)) type = Column(String(50)) __mapp
列执行一个过滤器。我无法确定这是否真的可以做到
首先,让我们使用同一个继承示例,该示例来自刚刚稍加修改的。我省略了这里的导入
class Employee(Base):
__tablename__ = 'employee'
id = Column(Integer, primary_key=True)
name = Column(String(50))
type = Column(String(50))
__mapper_args__ = {
'polymorphic_identity':'employee',
'polymorphic_on':type
}
@classmethod
def get_all(cls, session, query):
_filters = []
for prop in class_mapper(cls).iterate_properties:
if isinstance(prop, ColumnProperty):
_col = prop.columns[0]
_attr = getattr(cls, _cls.name)
_filters.append(cast(_attr, String).match(query))
result = session.query(cls)
result = result.filter(or_(*_filters))
return result.all()
class Engineer(Employee):
__tablename__ = 'engineer'
id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
engineer_name = Column(String(30))
foo = Column(String(10))
__mapper_args__ = {
'polymorphic_identity':'engineer',
}
class Manager(Employee):
__tablename__ = 'manager'
id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
manager_name = Column(String(30))
bar = Column(String(20))
__mapper_args__ = {
'polymorphic_identity':'manager',
}
现在让我们假设我想查询所有Employee
,其中一些字段与查询匹配。上面显示的方法get\u all
将只查询类Employee
已知的列
有什么方法可以查询整个继承链的所有列吗?这很难看,但有一种方法是找到从Employee继承的所有子类,然后左键联接这些表并将它们的列添加到查询中
如何获取子类:
我还没有测试过这个,但是类似的东西应该可以工作
@classmethod
def get_all(cls, session, query):
_filters = []
for prop in class_mapper(cls).iterate_properties:
if isinstance(prop, ColumnProperty):
_col = prop.columns[0]
_attr = getattr(cls, _cls.name)
_filters.append(cast(_attr, String).match(query))
result = session.query(cls)
result = result.filter(or_(*_filters))
# get the subclasses
subclasses = set()
for child in cls.__subclasses__():
if child not in subclasses:
subclasses.add(child)
# join the subclass
result = result.outerjoin(child)
# recurse to get the columns from the subclass
result = subclass.get_all(session, result)
# return a query, not a result to allow for the recursion.
# you might need to tweak this.
return result
事实上,这相当令人讨厌,但似乎是唯一的办法。谢谢你关于使用左连接的提示