#34597: Queryset (split) exclude's usage of Exists is significantly slower than
subquery
-------------------------------------+-------------------------------------
Reporter: Lorand Varga | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: 3.2
(models, ORM) |
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 David Sanders):
Posting some investigation here for charettes & others:
I suspect the additional redundant condition in the inner query that
references the outer query is causing unwanted materialisation:
{{{
AND "test_app_blog"."id" = "test_app_blog"."id"
}}}
When I removed this – no more materialisation.
Additionally: Not sure why this is being added to the query but if you
remove `Q(is_published=True)` so that you simply have
`Blog.objects.filter(~Q(translation=None))` then this redundant condition
is no longer added.
I tested with the reporter's models on latest main & I'd wager this is
something we can/may want to address.
--
Ticket URL: <https://code.djangoproject.com/ticket/34597#comment:6>
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