mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-12 03:38:35 -04:00
Mike Bayer
133 lines
3.7 KiB
Python
133 lines
3.7 KiB
Python
"""a basic Adjacency List model tree."""
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from sqlalchemy import *
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from sqlalchemy.util import OrderedDict
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metadata = BoundMetaData('sqlite:///', echo=True)
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trees = Table('treenodes', metadata,
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Column('node_id', Integer, Sequence('treenode_id_seq',optional=False), primary_key=True),
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Column('parent_node_id', Integer, ForeignKey('treenodes.node_id'), nullable=True),
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Column('node_name', String(50), nullable=False),
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)
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class NodeList(OrderedDict):
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"""subclasses OrderedDict to allow usage as a list-based property."""
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def append(self, node):
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self[node.name] = node
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def __iter__(self):
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return iter(self.values())
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class TreeNode(object):
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"""a rich Tree class which includes path-based operations"""
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def __init__(self, name):
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self.children = NodeList()
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self.name = name
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self.parent = None
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self.id = None
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self.parent_id = None
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def append(self, node):
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if isinstance(node, str):
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node = TreeNode(node)
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node.parent = self
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self.children.append(node)
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def __repr__(self):
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return self._getstring(0, False)
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def __str__(self):
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return self._getstring(0, False)
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def _getstring(self, level, expand = False):
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s = (' ' * level) + "%s (%s,%s, %d)" % (self.name, self.id,self.parent_id,id(self)) + '\n'
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if expand:
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s += ''.join([n._getstring(level+1, True) for n in self.children.values()])
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return s
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def print_nodes(self):
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return self._getstring(0, True)
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mapper(TreeNode, trees, properties=dict(
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id=trees.c.node_id,
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name=trees.c.node_name,
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parent_id=trees.c.parent_node_id,
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children=relation(TreeNode, cascade="all", backref=backref("parent", remote_side=[trees.c.node_id]), collection_class=NodeList),
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))
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print "\n\n\n----------------------------"
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print "Creating Tree Table:"
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print "----------------------------"
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trees.create()
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node2 = TreeNode('node2')
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node2.append('subnode1')
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node = TreeNode('rootnode')
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node.append('node1')
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node.append(node2)
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node.append('node3')
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node.children['node2'].append('subnode2')
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print "\n\n\n----------------------------"
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print "Created new tree structure:"
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print "----------------------------"
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print node.print_nodes()
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print "\n\n\n----------------------------"
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print "Flushing:"
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print "----------------------------"
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session = create_session()
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session.save(node)
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session.flush()
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print "\n\n\n----------------------------"
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print "Tree After Save:"
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print "----------------------------"
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print node.print_nodes()
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node.append('node4')
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node.children['node4'].append('subnode3')
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node.children['node4'].append('subnode4')
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node.children['node4'].children['subnode3'].append('subsubnode1')
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del node.children['node1']
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print "\n\n\n----------------------------"
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print "Modified the tree"
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print "(added node4, node4/subnode3, node4/subnode4,"
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print "node4/subnode3/subsubnode1, deleted node1):"
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print "----------------------------"
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print node.print_nodes()
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print "\n\n\n----------------------------"
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print "Flushing:"
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print "----------------------------"
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session.flush()
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print "\n\n\n----------------------------"
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print "Tree After Save:"
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print "----------------------------"
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print node.print_nodes()
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nodeid = node.id
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print "\n\n\n----------------------------"
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print "Clearing session, selecting "
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print "tree new where node_id=%d:" % nodeid
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print "----------------------------"
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session.clear()
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t = session.query(TreeNode).select(TreeNode.c.id==nodeid)[0]
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print "\n\n\n----------------------------"
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print "Full Tree:"
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print "----------------------------"
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print t.print_nodes()
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print "\n\n\n----------------------------"
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print "Marking root node as deleted"
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print "and flushing:"
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print "----------------------------"
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session.delete(t)
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session.flush()
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