mirror of
https://github.com/coleifer/peewee.git
synced 2026-05-06 07:56:41 -04:00
Charles Leifer
735ff26b47
This improves the way prefetch() works with model aliases. Also included an adjacency list example similar to the one in SQA.
59 lines
1.5 KiB
Python
59 lines
1.5 KiB
Python
from peewee import *
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db = SqliteDatabase(':memory:')
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class Node(Model):
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name = TextField()
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parent = ForeignKeyField('self', backref='children', null=True)
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class Meta:
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database = db
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def __str__(self):
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return self.name
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def dump(self, _indent=0):
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return (' ' * _indent + self.name + '\n' +
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''.join(child.dump(_indent + 1) for child in self.children))
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db.create_tables([Node])
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tree = ('root', (
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('n1', (
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('c11', ()),
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('c12', ()))),
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('n2', (
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('c21', ()),
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('c22', (
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('g221', ()),
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('g222', ()))),
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('c23', ()),
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('c24', (
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('g241', ()),
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('g242', ()),
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('g243', ())))))))
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stack = [(None, tree)]
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while stack:
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parent, (name, children) = stack.pop()
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node = Node.create(name=name, parent=parent)
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for child_tree in children:
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stack.insert(0, (node, child_tree))
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# Now that we have created the stack, let's eagerly load 4 levels of children.
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# To show that it works, we'll turn on the query debugger so you can see which
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# queries are executed.
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import logging; logger = logging.getLogger('peewee')
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logger.addHandler(logging.StreamHandler())
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logger.setLevel(logging.DEBUG)
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C = Node.alias('c')
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G = Node.alias('g')
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GG = Node.alias('gg')
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GGG = Node.alias('ggg')
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roots = Node.select().where(Node.parent.is_null())
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pf = prefetch(roots, C, (G, C), (GG, G), (GGG, GG))
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for root in pf:
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print(root.dump())
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