Hello.
Suppose I have the following mapped classes, A and B, that have two distinct M:N
relationships, AB1 and AB2. If A.x is null, only relations in AB1 apply. If it
is not null, only relations in AB2 apply. A also has 1:N relationship to C (one
A can have more Cs). Finally, A is infact a joined table inheritance superclass
with two subclasses, A1 and A2. I want to select all As for a given B via AB1 or
AB2. I also want to prefetch A.cs of the results using joinedload. I use the
code like this:
q1 = session.query(A).with_polymorphic([A1, A2])
q1 = q1.filter(exists().where(and_(
A.x == None,
AB1.a_id == A.id,
AB1.b_id == b_id, # input argument
))
q2 = session.query(A).with_polymorphic([A1, A2])
q2 = q2.filter(exists().where(and_(
A.x != None,
AB2.a_id == A.id,
AB2.b_id == b_id, # input argument,
))
q = q1.union_all(q2)
q = q.options(
joinedload(A.cs),
)
return q
This creates the following SQL:
SELECT ....
FROM (
SELECT... -- via AB1
UNION ALL
SELECT ... -- via AB2
) anon_1
LEFT OUTER JOIN c ON c.a_id = a.id -- error line
This fails with a missing from clause error for table a. The attribute a.id is
actually anon_1.a_id.
What am I doing wrong? / How can I fix this?
Thank you in advance,
Ladislav Lenart
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