mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-11 11:22:15 -04:00
Mike Bayer
130 lines
3.7 KiB
Python
130 lines
3.7 KiB
Python
"""A basic Adjacency List model tree."""
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from sqlalchemy import MetaData, Table, Column, Sequence, ForeignKey
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from sqlalchemy import Integer, String
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from sqlalchemy.orm import create_session, mapper, relation, backref
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from sqlalchemy.orm.collections import attribute_mapped_collection
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metadata = MetaData('sqlite:///')
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metadata.bind.echo = True
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trees = Table('treenodes', metadata,
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Column('id', Integer, Sequence('treenode_id_seq', optional=True),
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primary_key=True),
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Column('parent_id', Integer, ForeignKey('treenodes.id'), nullable=True),
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Column('name', String(50), nullable=False))
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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.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[node.name] = 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)" % (
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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)
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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={
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'children': relation(TreeNode, cascade="all",
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backref=backref("parent", remote_side=[trees.c.id]),
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collection_class=attribute_mapped_collection('name'),
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lazy=False, join_depth=3)})
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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).filter(TreeNode.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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