如何在sqlalchemy的邻接表中将子节点添加到父节点？

Question

I was looking at the example below. My program is setup similar but without the backref. I want a one-to-many relationship. Children need not know their parents. I am just a but confused as the line "node = TreeNode('rootnode')", wouldn't that be ran everytime the program is executed and possibly create duplicates?

How do you add a subnode without the parent backref?

I see for example the following

node = TreeNode('rootnode')
TreeNode('node1', parent=node)

node1 is created with name 'node1' and it's parent is passed alone. parent is defined in the children relationship as

backref("parent", remote_side=id)

I don't much need children to know parents, just parents knowing children. How do you create the relationship so parents know children?

http://docs.sqlalchemy.org/en/latest/_modules/examples/adjacency_list/adjacency_list.html

Answer 1

rootnode = TreeNode('rootnode')
# assign "children" attribute straight away:
node1 = TreeNode('node1', 
    children=[TreeNode('node1.child1'), TreeNode('node1.child2')]
    )
# or just manipulate as any regular list
rootnode.children.append(node1)

---

I the example you link to parent already knows children by the fact that the relationship children is defined:

children = relationship("TreeNode", # NOTE: now each TreeNode has "children"
                    # ...
                    backref=backref("parent", remote_side=id), # this line allows children to link to "parent"
                    # ...
                )

Therefore