#35102: Performance regression on Model.objects.count() between Django 4.2 and
5.0
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Reporter: Anthony Shaw | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 5.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Mariusz Felisiak):
Thanks for the report, I think we could make it faster by avoiding cloning
every time:
{{{#!diff
diff --git a/django/db/models/expressions.py
b/django/db/models/expressions.py
index c20de5995a..80b8fc8e6a 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -404,8 +404,9 @@ class BaseExpression:
def replace_expressions(self, replacements):
if replacement := replacements.get(self):
return replacement
+ if not (source_expressions := self.get_source_expressions()):
+ return self
clone = self.copy()
- source_expressions = clone.get_source_expressions()
clone.set_source_expressions(
[
expr.replace_expressions(replacements) if expr else None
}}}
Does it work for you?
--
Ticket URL: <https://code.djangoproject.com/ticket/35102#comment:2>
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