#32549: Make `Q(Q(), ...)` equivalent to `Q(...)`
-------------------------------------+-------------------------------------
Reporter: jonathan- | Owner: nobody
golorry |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: dev
layer (models, ORM) | Keywords: Q objects, nested,
Severity: Normal | empty
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
Empty Q objects (`Q()` or `~Q()`, etc) evaluate to `False`, but `Q(Q())`
evaluates to `True`. This interferes with the shortcut on logical
operations involving empty Q objects and can lead to bugs when trying to
detect empty operations.
{{{
def q_any(iterable):
q = Q()
for element in iterable:
q |= element
if q:
return q
return Q(pk__in=[])
Item.objects.filter(q_any()) # no items
Item.objects.filter(q_any([Q()])) # no items
Item.objects.filter(q_any([Q(Q())])) # all items
}}}
This patch removes empty Q objects from `args` during Q object
initialization.
This requires https://code.djangoproject.com/ticket/32548 in order to
prevent a regression in logical operations between query expressions and
empty Q objects.
--
Ticket URL: <https://code.djangoproject.com/ticket/32549>
Django <https://code.djangoproject.com/>
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