On 5/8/15 5:09 PM, Carlus wrote:
Yes exactly, imagine and hotel vanish, and it became into an
apartment, i know is a weird situation but the code is just an example.
OK so the ORM doesn't support an object changing into a new class in
place. You have to emit the UPDATE that you want, and since this is
joined inheritance, it means you have to emit the UPDATE, DELETE, and
INSERT across all three tables manually, using Core with
Session.execute(). Then you need to entirely re-load the object and
whatever else has it in a collection. When the ORM loads it fresh,
then it will be loaded as the new class.
example, we have these records:
Person table:
id = 1, person_name = "john", accommodation_id =1
accommodation table:
accommodation_id =1
accommodation_type = "hotel"
address = "street xxx"
hotel_name = "Hotel xxx"
So the idea is to get convert in:
accommodation_id =1 #dont need to be the same,
but need to keep the same relationship with Person table
accommodation_type = "apartment"
address = "street xxx" #keep the same
apartm_name = "Apartment xxx" #delete fields from Hotel
table and add from Apartment table
I hope now is a little more clear the example, but I said is just an
educative code :)
El viernes, 8 de mayo de 2015, 21:30:45 (UTC+2), Michael Bayer escribió:
On 5/8/15 2:41 PM, Carlus wrote:
Hello,
Sorry I couldnt find info about in google neither in the
documentation,
I have a model structure like this one:
class Person(Base):
__tablename__ ='person' id = Column(Integer, primary_key=True,
nullable=False)
person_name = Column(String, nullable=False)
accommodation_id = Column(Integer, ForeignKey("accommodation.id
<http://accommodation.id>"))
accommodation = relationship("Accommodation", backref="people")
def __init__(self, person_name):
self.person_name = person_name
class Accommodation(Base):
__tablename__ ='accommodation' __mapper_args__ =
{'polymorphic_identity':'accommodation',
'polymorphic_on':'accommodation_type'}id = Column(Integer, primary_key=True)
accommodation_type = Column(String(32))
address = Column(String)
class Hotel(Accommodation):
__tablename__ ='hotel' __mapper_args__ = {'polymorphic_identity':'hotel' }id
= Column(Integer, ForeignKey('accommodation.id <http://accommodation.id>'),
primary_key=True)
hotel_name = Column(String)
def __init__(self, name, address):
self.hotel_name = name
self.address = address
class Apartment(Accommodation):
__tablename__ ='apartment' __mapper_args__ =
{'polymorphic_identity':'apartment' }id = Column(Integer,
ForeignKey('accommodation.id <http://accommodation.id>'), primary_key=True)
apartm_name = Column(String)
def __init__(self, name, address):
self.apartm_name = name
self.address = address
Where each Person is associate to some accommodation (thanks to
polymorphic can be Hotel or Apartment), each accommodation can
have more than one Person. Im having problems when I try to
update some record in the table accommodation, mainly when for
example updating the accomodation_type (an Apartment became into
a Hotel, where would get new records in Hotel and would delete
any info from the record in Apartment and keeping the same id,
address, and relationship with People.
I'm not sure what angle you are coming from. Did you want to emit
an UPDATE for accomodation_type? That would be awkward; it means
a Hotel vanishes and becomes an Apartment. Do you mean, you just
want to take a Person, associated with some Hotel, and move that
Person to an Apartment? That would just be an UPDATE of
Person.accomodation_id. Just change the Person.accommodation
attribute to the parent record you want. Not sure what you mean.
You'd need to illustrate what rows you are looking to modify for
me to understand which one you are getting at.
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