On Apr 22, 2008, at 8:57 PM, David Gardner wrote:
>
> Thanks for your response, I ended up deciding that it was OK if leaf
> nodes show up as regular nodes. So I dropped my qry_node query, and
> kept
> the qry_leaf query, and it is working now.
>
> I should have mentioned as a side note, that my SA code needs to play
> nice with a closed source package, so I am not able to make schema
> level
> changes.
>
just FTR, a working version of the "two selects" mapping:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.orm.collections import attribute_mapped_collection
m = MetaData(create_engine('sqlite://', echo=True))
node_table = Table("n", m,
Column('id', Integer, primary_key=True),
Column('name', String(50)),
Column('type', String(50)),
Column('parent_id', Integer, ForeignKey('n.id'))
)
m.create_all()
qry_node = select ([node_table], node_table.c.type!
='file').alias('node_query')
qry_leaf = select ([node_table],
node_table.c.type=='file').alias('leaf_query')
class Node(object):
def __init__(self, name):
self.type='node'
self.name = name
class Leaf(object):
def __init__(self, name):
self.type='file'
self.name = name
mapper(Leaf, qry_leaf)
mapper(Node, qry_node, properties = {
'Children' : relation(Node,
cascade='all',collection_class=attribute_mapped_collection('name'),
backref=backref('Parent', remote_side=[qry_node.c.id])
),
'Files' :
relation(Leaf,primaryjoin=(qry_node.c.id==qry_leaf.c.parent_id),
order_by=qry_leaf.c.name, cascade='all,delete-orphan')
})
n1 = Node('n1')
n1.Parent = Node('n1parent')
n1.Files.append(Leaf('file1'))
n1.Files.append(Leaf('file2'))
sess = create_session()
sess.save(n1)
sess.flush()
sess.clear()
files =
sess.query(Node).filter_by(name='n1parent').one().Children['n1'].Files
assert [f.name for f in files] == ['file1', 'file2']
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