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gh-158816: Skip useless hash table probe when deleting from split dicts #158819

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gh-158816: Skip useless hash table probe when deleting from split dicts #158819

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gh-158816: Skip redundant hash table probe when deleting from split d…
hetaozdh Oct 5, 2026
4d6a6ee
Merge branch 'main' into dict_delitem_common_optimization
hetaozdh Oct 5, 2026
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-10-04-20-04-55.gh-issue-158816.9ulhWb.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Speed up deleting items from split dictionaries (for example the
materialized ``__dict__`` of an instance with inline values) by skipping a
redundant hash table probe.
6 changes: 3 additions & 3 deletions Objects/dictobject.c
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Expand Up @@ -2938,9 +2938,6 @@ delitem_common(PyDictObject *mp, Py_hash_t hash, Py_ssize_t ix,

PyObject *old_key;

Py_ssize_t hashpos = lookdict_index(mp->ma_keys, hash, ix);
assert(hashpos >= 0);

STORE_USED(mp, mp->ma_used - 1);
if (_PyDict_HasSplitTable(mp)) {
assert(old_value == mp->ma_values->values[ix]);
Expand All @@ -2951,6 +2948,9 @@ delitem_common(PyDictObject *mp, Py_hash_t hash, Py_ssize_t ix,
ASSERT_CONSISTENT(mp);
}
else {
Py_ssize_t hashpos = lookdict_index(mp->ma_keys, hash, ix);
assert(hashpos >= 0);

FT_ATOMIC_STORE_UINT32_RELAXED(mp->ma_keys->dk_version, 0);
dictkeys_set_index(mp->ma_keys, hashpos, DKIX_DUMMY);
if (DK_IS_UNICODE(mp->ma_keys)) {
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