#31792: Use `EXISTS(SELECT 1 ...)` for subqueries
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Reporter: w0rp | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Uncategorized | Version: 3.0
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
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Changes (by Simon Charette):
* type: Uncategorized => Cleanup/optimization
* stage: Unreviewed => Accepted
Comment:
I could swear there was another ticket about that but I cannot find it.
The logic to clear the column is a bit more complex than what you've
described here but it's all detailed in `Query.has_results`
[https://github.com/django/django/blob/156a2138db20abc89933121e4ff2ee2ce56a173a/django/db/models/sql/query.py#L526-L535
(link)] and `SQLCompiler.has_results`
[https://github.com/django/django/blob/156a2138db20abc89933121e4ff2ee2ce56a173a/django/db/models/sql/compiler.py#L1129-L1130
(link)] so it could be added to `Exists.as_sql`.
Ideally the logic would be encapsulated in a `Query` method so it doesn't
have to be duplicated in `Query.has_results` and `Exists.as_sql` so both
could path could benefit from optimizations such as #24296.
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Ticket URL: <https://code.djangoproject.com/ticket/31792#comment:1>
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