#35102: Performance regression on Model.objects.count() between Django 4.2 and
5.0
-------------------------------------+-------------------------------------
Reporter: Anthony Shaw | Owner: (none)
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: 5.0
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Simon Charette):
Alternate patch that avoids the cost at class definition time as that
might have an effect on Django bootstrapping time
{{{#!diff
diff --git a/django/db/models/expressions.py
b/django/db/models/expressions.py
index c20de5995a..0ecda38353 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -14,7 +14,7 @@
from django.db.models.constants import LOOKUP_SEP
from django.db.models.query_utils import Q
from django.utils.deconstruct import deconstructible
-from django.utils.functional import cached_property
+from django.utils.functional import cached_property, classproperty
from django.utils.hashable import make_hashable
@@ -485,15 +485,21 @@ def select_format(self, compiler, sql, params):
class Expression(BaseExpression, Combinable):
"""An expression that can be combined with other expressions."""
+ @classproperty
+ @functools.lru_cache(maxsize=128)
+ def _constructor_signature(cls):
+ return inspect.signature(cls.__init__)
+
@cached_property
def identity(self):
- constructor_signature = inspect.signature(self.__init__)
args, kwargs = self._constructor_args
- signature = constructor_signature.bind_partial(*args, **kwargs)
+ signature = self._constructor_signature.bind_partial(self, *args,
**kwargs)
signature.apply_defaults()
arguments = signature.arguments.items()
identity = [self.__class__]
for arg, value in arguments:
+ if arg == 'self':
+ continue
if isinstance(value, fields.Field):
if value.name and value.model:
value = (value.model._meta.label, value.name)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/35102#comment:13>
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