I'm sure this is something fairly basic, but I'm stumped at this
point. I have a single table inheritance scheme setup very similar to
this:
class SimpleType(object):
def __init__(self, type='base_type', name='base_type'):
self.type = type
self.name = name
class AddressType(SimpleType):
type = 'Address'
def __init__(self, name):
SimpleType.__init__(self, 'Address', name)
class ContactType(SimpleType):
type = 'Contact'
def __init__(self, name):
SimpleType.__init__(self, 'Contact', name)
types_table = Table('types', metadata,
Column('type' , String(20), primary_key=True),
Column('name' , String(20), primary_key=True)
)
mapper(SimpleType, self.types_table,
polymorphic_on=self.types_table.c.type,
polymorphic_identity='base_type')
mapper(AddressType, self.types_table,
inherits=types_mapper,
polymorphic_identity='Address')
mapper(ContactType, self.types_table,
inherits=types_mapper,
polymorphic_identity='Contact')
My question is about querying. Is the expected behaviour of
"session.query(AddressType)" to return all values from the 'types'
table? (i.e. for me this returns all AddressType and ContactType
values from the table)? If so, is there a standard or preferred
method of getting just those values associated with one class without
hardcoding the classes polymorphic_identity value into the query? For
instance, "session.query(AddressType).filter_by(type='Address')"
works, but "session.query(AddressType).filter_by
(type=AddressType.type)" does not. I'd really like to wrap up this
type of query in a simple call to the class type.
Any suggestions greatly appreciated.
Thanks,
Mark
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