Hi
Thanks for the hint.
FYI: Finally i decided to use hybrid_property and conditional logic
using this model
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
}
@hybrid_property
def POLYMORPHICLS(self):
return func.concat(self.__name__)
@POLYMORPHICLS.expression
def POLYMORPHICLS(self):
return case([
( self.type == 'engineer',
func.concat(self.__mapper__.polymorphic_map['engineer'].class_.__name__)),
( self.type == 'manager',
func.concat(self.__mapper__.polymorphic_map['manager'].class_.__name__))
],
else_ = func.concat(self.__name__)
)
So I can do qury like this :
session.query(Employee.POLYMORPHICLS).filter(Employee.name=='Employee_Name'').all()
OR FILTER
session.query(Employee).filter(Employee.name=='Employee_Name',Employee.POLYMORPHICLS=='Manager').all()
I hope this is correct
Disadvantage:
I have to specify all the existing inherited class type in
@POLYMORPHICLS.expression
Regards
G
On Tuesday, June 2, 2015 at 6:30:44 PM UTC+2, g wrote:
>
> 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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