#34603: ~Q() incorrectly interpreted as full rather than empty
-------------------------------------+-------------------------------------
Reporter: Anders Kaseorg | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution: wontfix
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 Anders Kaseorg):
There’s an important difference between ''including'' nothing and
''excluding'' nothing. We can’t just say these are the same because they
both involve “nothing”.
- `Q()` matches every row that satisfies no particular restrictions—i.e.,
it matches every row. (In Python, `all([]) == True`.)
- `~Q()` should match everything ''other than'' the rows that satisfy no
particular restrictions–i.e., it should match no rows. (In Python,
`not(all([])) == False`.)
I know this is a dense explanation that’s hard to digest in this abstract
form. But the rules of formal logic do give us a right answer here; this
is not some ambiguous question of philosophy.
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Ticket URL: <https://code.djangoproject.com/ticket/34603#comment:4>
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