On 01/17/2017 01:05 PM, Chris Withers wrote:
Potentially related issue, given:
class TheTable(Base):
__tablename__ = 'stuff'
__mapper_args__ = dict(
polymorphic_on='type',
polymorphic_identity='base',
)
type = Column(String)
col = Column(String)
class Model1(TheTable):
__mapper_args = dict(
polymorphic_identity='model1',
)
class Model2(TheTable):
__mapper_args = dict(
polymorphic_identity='model2',
)
session.add(Model1(col='a'))
session.add(Model2(col='b'))
session.flush()
I'd now expect:
self.session.query(Model1)
...to turn the Model1 instance, but in my tests it returns nothing.
you misspelled "__mapper_args__"
self.session.query(TheTable) returns both rows, but both as TheTable
instances, which I find a little surprising.
Chris
On 16/01/2017 17:54, mike bayer wrote:
issue
https://bitbucket.org/zzzeek/sqlalchemy/issues/3891/single-inh-criteria-should-be-added-for
is added. Targeted at 1.2 as it will break applications unknowingly
relying upon the bug right now.
For now say func.count(Manager.employee_id), e.g. put the entity in the
columns clause.
On 01/16/2017 12:23 PM, Michael Williamson wrote:
Hello!
I have a use case where I want to select from a polymorphic table, but
without selecting any columns from that table. As a simple example,
consider selecting the count of all rows. When I write something like:
sess.query(func.count(1)).select_from(Manager).all()
It seems to be equivalent to:
sess.query(func.count(1)).select_from(Employee).all()
(where Manager inherits from Employee).
Is this intended, or is this a bug? If the former, what's the suggested
approach to writing such queries? To filter on the discriminator
explicitly?
For reference, I was able to reproduce the issue with a test case in
test/orm/inheritance/test_single.py:
def test_select_from_inherited_tables(self):
Manager, Engineer, Employee = (self.classes.Manager,
self.classes.Engineer, self.classes.Employee)
sess = create_session()
m1 = Manager(name='Tom', manager_data='data1')
e1 = Engineer(name='Kurt', engineer_info='knows how to hack')
sess.add_all([m1, e1])
sess.flush()
eq_(
sess.query(func.count(1)).select_from(Manager).all(),
[(1, )]
)
Thanks
Michael
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