#32632: Query resolution can be at least 3x slower in 3.2
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Reporter: mrfleap | Owner: nobody
Type: Bug | Status: new
Component: Database | Version: 3.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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I recently upgraded to Django 3.2 from 3.1.8 and found running my queries
were taking nearly 15 seconds to run compared to a few milliseconds in
3.1.8. To help bring this issue to light I've created a basic Django
project on GitHub with a test case that shows this issue. Running
"manage.py test" on Django 3.2 and Django 3.1.8 shows that 3.2 is taking
roughly 3x as long to build the query, while not executing the query.
Repository with test case: https://github.com/mrfleap/django-db-test
The underlying query is admittedly repetitive, but I still feel it this
degradation in performance should not go overlooked. Through some basic
debugging I believe the issue may lie django/utils/tree.py on line 93
(https://github.com/django/django/blob/stable/3.2.x/django/utils/tree.py#L93)
where it checks to see if a node is within a list of children, one of my
basic tests found the operation to take 9 seconds alone, rather than the
fractions of a millisecond it usually takes. I've attached a screenshot of
my breakpoint to showcase that it's taking ~9 seconds to determine if one
node exists in an array of two.
I'd also like to point out that I am using Django Guardian quite heavily
in this scenario, which is leading to the complicated query in the first
place. However, as far as I am aware, there is no difference in the
generated query between both versions, and the difference in speed is
based on how Django is resolving the internal objects into a SQL
statement.
Please let me know if there's any other information I can provide to help
fix this issue.
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Ticket URL: <https://code.djangoproject.com/ticket/32632>
Django <https://code.djangoproject.com/>
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