Hi all
Is there a way to get the "classname" of the polymorphic class result in a
single query on the base class ?
soemthing like this
session.query(cast(Employee.__mapper__.polymorphic_map[Employee.type].class_.__name__,
String)).filter(Employee.name=='Employee_Name').one()
*Details *
*=======*
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import aliased
from sqlalchemy.ext.hybrid import hybrid_property
Base = declarative_base()
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
}
class Engineer(Employee):
__tablename__ = 'engineer'
id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
engineer_name = Column(String(30))
__mapper_args__ = {
'polymorphic_identity':'engineer',
}
class Manager(Employee):
__tablename__ = 'manager'
id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
manager_name = Column(String(30))
__mapper_args__ = {
'polymorphic_identity':'manager',
}
e = create_engine('postgresql+psycopg2://uuuu:****@host/test', echo=False)
Base.metadata.create_all(e)
session = Session(e)
*WITH THIS DATA*
*===============*
eng = Engineer(name= 'Employee_Name', engineer_name= 'Engineer_name')
session.add(eng)
session.commit()
*SIMPLE QUERY *
*==============*
empl = session.query(Employee).filter(Employee.name=='Employee_Name').one()
print empl <__main__.Engineer at 0x6573c50>
BUT WHAT I WANT IS ONLY THE CLASS NAME OF POLYMORPHIC CLASS SO I TRIED THIS
employee =
session.query(cast(Employee.__mapper__.polymorphic_map['employee'].class_.__name__,
String)).filter(Employee.name=='Employee_Name').one() print(employee) =>
(u'Employee',)
and with
e =
session.query(cast(Employee.__mapper__.polymorphic_map['engineer'].class_.__name__,
String)).filter(Employee.name=='Employee_Name').one()
print(e)
AND finally to generalize i tried:
e =
session.query(cast(Employee.__mapper__.polymorphic_map[Employee.type].class_.__name__,
String)).filter(Employee.name=='Employee_Name').one() print(e)
---------------------------------------------------------------------------KeyError
Traceback (most recent call
last)<ipython-input-31-45f6c96837bf> in <module>() 1 #generalize----> 2 e
=
session.query(cast(Employee.__mapper__.polymorphic_map[Employee.type].class_.__name__,
String)).filter(Employee.name=='EN').one() 3 print(e)
KeyError: <sqlalchemy.orm.attributes.InstrumentedAttribute object at 0x0654FD80>
I think i am doing something logically wrong .
QUESTION
========
Is there a way to get the classname of the polymorphic class result in a
single query ?
I tried with hybrid_property but i had the same error
Some hints ?
Regards
G
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