Hi All!
Assume we have the following setup:
a_table = Table('A', metadata,
Column('id', Integer, primary_key=True)
)
b_table = Table('B', metadata,
Column('id', Integer, primary_key=True),
Column('parent_b1_id', Integer, ForeignKey('B.id')),
Column('parent_a_id', Integer, ForeignKey
(a_table.c.id)),
Column('parent_b2_id', Integer, ForeignKey('B.id')))
mapper(A,a_table)
mapper(B,b_table,properties = {
'parent_b1': relation(B,
lazy = True,
remote_side = [b_table.c.id],
join_depth = 1,
primaryjoin = (b_table.c.parent_b1_id ==
b_table.c.id)),
'parent_z': relation(A,lazy = True),
'parent_b2': relation(B,
lazy = True,
remote_side = [b_table.c.id],
join_depth = 1,
primaryjoin = (b_table.c.parent_b2_id ==
b_table.c.id))
});
#and lets do perform a query:
session.query(B).options(eagerload('parent_b1'),eagerload
('parent_b2'),eagerload('parent_z')).all()
#the query gives us the following output (MySQL)
"""
SELECT ...
FROM `B`
LEFT OUTER JOIN `B` AS `B_1` ON `B`.parent_b1_id = `B_1`.id
LEFT OUTER JOIN `B` AS `B_2` ON `B_1`.parent_b2_id = `B_2`.id
LEFT OUTER JOIN `A` AS `A_1` ON `A_1`.id = `B_2`.parent_a_id
"""
Take a look at the last join - it gives me the B->B_2-A, but I asked
for B-A,
BTW, note this 'parent_z' notation, change to 'parent_a' and you will
get the following joins:
LEFT OUTER JOIN `A` AS `A_1` ON `A_1`.id = `B`.parent_a_id
LEFT OUTER JOIN `B` AS `B_1` ON `B`.parent_b1_id = `B_1`.id
LEFT OUTER JOIN `B` AS `B_2` ON `B_1`.parent_b2_id = `B_2`.id
Now the last join gives me B->B_1->B->2 instead of B->B_2
I tried but could not change this behavior, except turning Lazy off,
is there something I miss or it's a bug?
P.S.
I'm using sqlalchemy 0.5 rc4, db server MySQL
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