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bpo-32623: Resize dict after del/pop #5300

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methane wants to merge 1 commit into from
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bpo-32623: Resize dict after del/pop #5300

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21 changes: 20 additions & 1 deletion Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1475,6 +1475,17 @@ _PyDict_SetItem_KnownHash(PyObject *op, PyObject *key, PyObject *value,
return insertdict(mp, key, hash, value);
}

// Resize dict if dk_size is too large.
static int
after_removed(PyDictObject *mp)
{
if (mp->ma_keys->dk_size > PyDict_MINSIZE &&

@vstinner vstinner Jan 24, 2018

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Oh, I hesitated to propose the same test in your previous PR #5297, but I wasn't sure if it was required in practice since MINSIZE=8.

I like the idea of being explicit here, check size > MINSIZE.

mp->ma_used < mp->ma_keys->dk_size / 8) {
return insertion_resize(mp);
}
return 0;
}

static int
delitem_common(PyDictObject *mp, Py_hash_t hash, Py_ssize_t ix,
PyObject *old_value)
Expand All @@ -1497,7 +1508,7 @@ delitem_common(PyDictObject *mp, Py_hash_t hash, Py_ssize_t ix,
Py_DECREF(old_value);

assert(_PyDict_CheckConsistency(mp));
return 0;
return after_removed(mp);
}

int
Expand Down Expand Up @@ -1767,6 +1778,10 @@ _PyDict_Pop_KnownHash(PyObject *dict, PyObject *key, Py_hash_t hash, PyObject *d
Py_DECREF(old_key);

assert(_PyDict_CheckConsistency(mp));
if (after_removed(mp) < 0) {
Py_DECREF(old_value);

@vstinner vstinner Jan 24, 2018

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I'm not sure that it's ok to drop the popped value here :-(

If shrinking the dict fails, I suggest to ignore the error and return the old value anyway. The next del/pop will try again to shrink the dict.

return NULL;
}
return old_value;
}

Expand Down Expand Up @@ -2950,6 +2965,10 @@ dict_popitem(PyDictObject *mp)
mp->ma_used--;
mp->ma_version_tag = DICT_NEXT_VERSION();
assert(_PyDict_CheckConsistency(mp));
if (after_removed(mp) < 0) {
Py_DECREF(res);
return NULL;
}
return res;
}

Expand Down