Hi guys,
I’m to build an adjacency list in SA and have looked at the
basic_tree.py example provided, however, I need to order the children.
Now I don’t really want to use nested sets and I know linked lists can
be implemented in SA quite easily.
So naturally I tried something like
trees = Table('treenodes', metadata,
Column('id', Integer, Sequence('treenode_id_seq', optional=True),
primary_key=True),
Column('parent_id', Integer, ForeignKey('treenodes.id'),
nullable=True),
Column('name', String(50), nullable=False),
Column('next_id', Integer, ForeignKey('treenodes.id'),
unique=True, nullable=True)
)
mapper(TreeNode, trees, properties={
'children': relation(TreeNode, cascade="all",
backref=backref("parent", remote_side=
[trees.c.id]),
collection_class=attribute_mapped_collection('name'),
lazy=False, join_depth=3),
'next' : relation(TreeNode, uselist=False,
remote_side=trees.c.id,
backref=backref('previous',
uselist=False))}
)
Of course this does not work as it's a many to many relation (and so
needs another table). I would really prefer if I could get away with
just using one table though. Is there a way to do it?
Thanks.
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