#17712: <model>.objects.none() not always empty
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Reporter: ventur40 | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.3
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: none(), orm, | Needs documentation: 0
queryset, emptyqueryset | Patch needs improvement: 0
Has patch: 0 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by akaariai):
I don't believe .none().annotate() has this problem. I haven't tried but
it is hard to see how that could happen with the current code. Of course,
if you have value/values_list in between, then you have problems.
I think the best way forward would be to remove the `EmptyQuerySet`
altogether. Add a flag to sql.query and a couple of checks in the
different compiler/as_sql() methods or into the
models.query.`QuerySet`.iterator(). Or just add `NothingNode` into the
query.where. The latter is done in the patch attached to #17681. There
aren't many needed changes, at least not in the `NothingNode` case.
The downside of either of the above is that the operations on an empty
queryset are going to be somewhat slower (they actually do something). The
upside is that this kind of bug should be less common, and that the
queryset actually behaves exactly like the "real" queryset, which is not
the case at all now. In addition you get to remove around 200 lines of
code.
If you want to be technically correct when fixing this ticket and avoid
the `EmptyQuerySet` removal you should add `EmptyValuesQuerySet` and
`EmptyValuesListQuerySet` classes. I don't like that at all. You could
cheat and do "return self" from values and values_list however.
I wonder if there are something which I am missing about `EmptyQuerySet`.
Backward compatibility perhaps?
Should we deal with the `EmptyQuerySet` removal in a different ticket, or
hijack this one?
--
Ticket URL: <https://code.djangoproject.com/ticket/17712#comment:3>
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