1
0
mirror of https://github.com/django/django.git synced 2024-12-24 18:16:19 +00:00

Fixes #23837: Replace list.pop(0) by deque.popleft() in dfs function in migrations

This commit is contained in:
Niels Kouwenhoven 2014-11-15 16:34:20 +01:00
parent 83d104d61a
commit fefb77934e

View File

@ -1,4 +1,5 @@
from __future__ import unicode_literals
from collections import deque
from django.db.migrations.state import ProjectState
from django.utils.datastructures import OrderedSet
@ -100,26 +101,28 @@ class MigrationGraph(object):
def dfs(self, start, get_children):
"""
Dynamic programming based depth first search, for finding dependencies.
Iterative depth first search, for finding dependencies.
"""
visited = []
visited = deque()
visited.append(start)
path = [start]
stack = sorted(get_children(start))
stack = deque(sorted(get_children(start)))
while stack:
node = stack.pop(0)
node = stack.popleft()
if node in path:
raise CircularDependencyError()
path.append(node)
visited.insert(0, node)
children = sorted(get_children(node))
visited.appendleft(node)
children = sorted(get_children(node), reverse=True)
# reverse sorting is needed because prepending using deque.extendleft
# also effectively reverses values
if not children:
path = []
stack = children + stack
stack.extendleft(children)
return list(OrderedSet(visited))