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[3.14] gh-142145: Remove quadratic behavior in node ID cache clearing (GH-142146) #142209

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Merged
gpshead merged 2 commits into from
Dec 3, 2025
+20 −8
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[3.14] gh-142145: Remove quadratic behavior in node ID cache clearing (GH-142146) #142209

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fe268f9
gh-142145: Remove quadratic behavior in node ID cache clearing (GH-14…
sethmlarson Dec 3, 2025
3671bdb
Merge branch '3.14' into backport-08d8e18-3.14
sethmlarson Dec 3, 2025
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gh-142145: Remove quadratic behavior in node ID cache clearing (GH-14… 
…2146)

* Remove quadratic behavior in node ID cache clearing

Co-authored-by: Jacob Walls <[email protected]>

* Add news fragment

---------
(cherry picked from commit 08d8e18)

Co-authored-by: Seth Michael Larson <[email protected]>
Co-authored-by: Jacob Walls <[email protected]>
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@sethmlarson @jacobtylerwalls @miss-islington
2 people authored and miss-islington committed Dec 3, 2025
commit fe268f9f6d2e501296621faeca0c101ddb76d880
18 changes: 18 additions & 0 deletions Lib/test/test_minidom.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

import copy
import pickle
import time
import io
from test import support
import unittest
Expand Down Expand Up @@ -173,6 +174,23 @@ def testAppendChild(self):
self.assertEqual(dom.documentElement.childNodes[-1].data, "Hello")
dom.unlink()

def testAppendChildNoQuadraticComplexity(self):
impl = getDOMImplementation()

newdoc = impl.createDocument(None, "some_tag", None)
top_element = newdoc.documentElement
children = [newdoc.createElement(f"child-{i}") for i in range(1, 2 ** 15 + 1)]
element = top_element

start = time.time()
for child in children:
element.appendChild(child)
element = child
end = time.time()

# This example used to take at least 30 seconds.
self.assertLess(end - start, 1)

def testAppendChildFragment(self):
dom, orig, c1, c2, c3, frag = self._create_fragment_test_nodes()
dom.documentElement.appendChild(frag)
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9 changes: 1 addition & 8 deletions Lib/xml/dom/minidom.py
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Expand Up @@ -292,13 +292,6 @@ def _append_child(self, node):
childNodes.append(node)
node.parentNode = self

def _in_document(node):
# return True iff node is part of a document tree
while node is not None:
if node.nodeType == Node.DOCUMENT_NODE:
return True
node = node.parentNode
return False

def _write_data(writer, text, attr):
"Writes datachars to writer."
Expand Down Expand Up @@ -1555,7 +1548,7 @@ def _clear_id_cache(node):
if node.nodeType == Node.DOCUMENT_NODE:
node._id_cache.clear()
node._id_search_stack = None
elif _in_document(node):
elif node.ownerDocument:
node.ownerDocument._id_cache.clear()
node.ownerDocument._id_search_stack= None

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Security/2025-12-01-09-36-45.gh-issue-142145.tcAUhg.rst
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@@ -0,0 +1 @@
Remove quadratic behavior in ``xml.minidom`` node ID cache clearing.
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