#28519: Add filter(), exclude(), and other base QuerySet methods to combined
QuerySets (union(), etc.)
-------------------------------------+-------------------------------------
Reporter: Stanislav Karpov | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: union, | Triage Stage: Accepted
intersection, difference |
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 harrim4n):
Until (if) this is implemented, I suggest adding a check when .get(),
.filter() etc. are called on such a QS. Currently the error messages (if
there are any) do not explain the issue, the only way to find out about
this is in the documentation of the QS API, section union().
Example:
{{{
qs1 = User.objects.all()
qs2 = User.objects.filter(username="nonexistant")
qs3 = qs1.difference(qs2)
print(qs1)
print(qs2)
print(qs3)
print(qs1.get(id=1))
print(qs3.get(id=1))
}}}
This fails with (could be any number instead of 4, of course)
{{{
MultipleObjectsReturned: get() returned more than one User -- it returned
4!
}}}
Even worse, if the difference of qs1 and qs2 only contains one element,
this element is returned when calling qs3.get(id=1) without any error
message, even though the objects ID is not 1.
--
Ticket URL: <https://code.djangoproject.com/ticket/28519#comment:4>
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