On Nov 8, 2006, at 12:04 AM, Randall Smith wrote:
That leads to the part I'm stuck on; mapper inheritance. When
finished,
session.query(Employee).select() should list all employee as instances
of their specific classes and session.query(Engineer).select() should
list all engineers ...
I worked on this some more and found that the queries are correct as
they are. The problem is in the mapping. A Chemical Engineer is an
Engineer, who is an Employee. So the employees selectable should return
all employees and the engineer selectable should return all engineers,
not just
hey, no, youre doing great, breaking new ground yourself. i havent
spent much time with inheritance scenarios other than what you see in
the examples and unittests (and a lot of that other people came up
with). just as long as the rowsets contain the information, things
are good. this is also
I've attached a file which is a variant to the employees example with
two objectives.
1. Base polymorphic_identity on select criteria (no type column).
2. Use two levels of inheritance.
The first objective seems to be met, but the second is not working
properly. I put in two Managers, two
if you change your echo to 'debug', or just select straight from your
p_union selectable, youll see these rows:
(5, u'cengineer1', u'cengineer1', u'cengineer1', None,
u'chemical_engineer')
(6, u'cengineer2', u'cengineer2', u'cengineer2', None,
u'chemical_engineer')
(1, u'manager1', None, None,
Randall Smith wrote:
For discussion, consider the Employee, Manager, Engineer example from
the docs. If I were designing the tables, I would not normally have a
type field. I would use the null status of engineer_info or
manager_data to determine the employee type. Or if that data was in
John,
Thanks for the feedback. The code I put up is not part of any real
system. I'm just playing off of the existing examples in the docs and
trying to get comfortable with SA inheritance.
Randall
John M Camara wrote:
Randall Smith wrote:
For discussion, consider the Employee,
just FYI, the type column idea is taken from Hibernate, and that's
all Hibernate supports as far as polymorphic loading.
But for polymorphic loading in SA, you are free to make any kind of
polymorphic_union you like that can add in a functionally-generated
type column, and specify it into
Michael Bayer wrote:
just FYI, the type column idea is taken from Hibernate, and that's
all Hibernate supports as far as polymorphic loading.
I think it's good that SA takes good features from and is similar to
Hibernate, but I hope that your aspirations and those of SA's users are
to make
