#24296: clear select fields for `.exists()` of distinct, non-sliced querysets
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Reporter: outofculture | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Database layer (models, ORM) | Version: 1.7
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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The fix (93cc6dcdac6fc3e506640fa38dd1798c3cd61cff) for bug #18414
introduced an inefficiency in `.exists()` on distinct querysets in that
now all distinct querysets are selecting all their fields. I propose the
fields should be left on the queryset only if `(q.distinct and
(q.high_mark is not None or q.low_mark is not None))`.
As I started writing the test for this, I realized I would have to inspect
the query itself, which seems... like a bad idea for a test. Would this be
reasonable to submit the (one-line-change) patch without a test, or does
someone have a suggestion for a way to make the test that's less brittle?
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Ticket URL: <https://code.djangoproject.com/ticket/24296>
Django <https://code.djangoproject.com/>
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