On 06/20/2017 02:08 PM, yoch.me...@gmail.com wrote:
Hi,
I wish to have a two-levels inheritance, but I don't know how to proceed.
The docs says that "only one discriminator column or SQL expression may
be configured for the entire inheritance hierarchy".
I tried with this example (mixing joined and single inheritances) :
|
classPerson(Base):
__tablename__ ='person'
id =Column(Integer,primary_key=True)
type =Column(String(50),nullable=False)
name =Column(String(50))
__mapper_args__ ={
'polymorphic_identity':'person',
'polymorphic_on':type
}
classManager(Person):
__tablename__ ='manager'
id =Column(ForeignKey('person.id'),primary_key=True)
manager_name =Column(String(30))
__mapper_args__ ={
'polymorphic_identity':'manager',
}
classEngineerBase(Person):
__tablename__ ='engineer'
id =Column(ForeignKey('person.id'),primary_key=True)
engineer_name =Column(String(30))
classEngineerType1(EngineerBase):
__mapper_args__ ={
'polymorphic_identity':'engineer_t1',
}
classEngineerType2(EngineerBase):
__mapper_args__ ={
'polymorphic_identity':'engineer_t2',
}
|
It seems to work, but it this correct ?
it's correct, you only have one "polymorphic_on" set up, and that's what
that means.
--
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http://www.sqlalchemy.org/
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