[Django] #26517: Empty Querset Using Empty Queryset in ExpressionWrapper
Django
----------------------------------------------+--------------------
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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We use the ExpressionWrapper + annotate to annotate specific boolean
values to all queried instances like this (minimal working example):
{{{
editable_ones = ..... # another queryset
result =
MyModel.objects.annotate(editable=ExpressionWrapper(Q(pk__in=editable_child_folders),
output_field=BooleanField())
}}}
As soon as {{{editable_ones}}} is empty, {{{result}}} is also empty.
Reading the docs, I guess this is not desired behavior
(https://docs.djangoproject.com/en/1.9/ref/models/querysets/#annotate).
--
Ticket URL: <https://code.djangoproject.com/ticket/26517>
Django <https://code.djangoproject.com/>
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Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by srkunze):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> We use the ExpressionWrapper + annotate to annotate specific boolean
> values to all queried instances like this (minimal working example):
>
> {{{
> editable_ones = ..... # another queryset
> result =
> MyModel.objects.annotate(editable=ExpressionWrapper(Q(pk__in=editable_child_folders),
> output_field=BooleanField())
> }}}
>
> As soon as {{{editable_ones}}} is empty, {{{result}}} is also empty.
> Reading the docs, I guess this is not desired behavior
> (https://docs.djangoproject.com/en/1.9/ref/models/querysets/#annotate).
New description:
We use the ExpressionWrapper + annotate to annotate specific boolean
values to all queried instances like this (minimal working example):
{{{
editable_ones = ..... # another queryset
result =
MyModel.objects.annotate(editable=ExpressionWrapper(Q(pk__in=editable_ones),
output_field=BooleanField())
}}}
As soon as {{{editable_ones}}} is empty, {{{result}}} is also empty.
Reading the docs, I guess this is not desired behavior
(https://docs.djangoproject.com/en/1.9/ref/models/querysets/#annotate).
--
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:1>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by srkunze):
I did some further analysis:
{{{
MyModel.objects.annotate(editable=ExpressionWrapper(Q(pk__in=MyModel.objects.none()),
output_field=BooleanField())
}}}
{{{
MyModel.objects.annotate(editable=ExpressionWrapper(Q(pk__in=MyModel.objects.filter(pk=-1)),
output_field=BooleanField())
}}}
Both results differ.
{{{MyModel.objects.none()}}} forces the outer query to return an empty
QuerySet.
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:2>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by charettes):
* version: 1.8 => master
* stage: Unreviewed => Accepted
Comment:
Related to or duplicate of both #26430 and #26433.
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:3>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by charettes):
* has_patch: 0 => 1
Comment:
[https://github.com/django/django/pull/6638 PR]
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:4>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by jarshwah):
FYI ExpressionWrapper was never meant to be used to wrap up Q() objects.
Q() are not really expressions themselves, they just implement some of the
same API internally.
You're much better off using Case Expressions
https://docs.djangoproject.com/en/1.9/ref/models/conditional-expressions/
for this use case:
{{{
MyModel.objects.annotate(editable=Case(When(pk__in=[editable], then=1),
default=0, output_field=BooleanField()) )
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:5>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by timgraham):
* needs_better_patch: 0 => 1
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:6>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by emulbreh):
* needs_better_patch: 1 => 0
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:7>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: new
(models, ORM) |
Severity: Normal | Resolution:
| checkin
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by timgraham):
* stage: Accepted => Ready for checkin
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:8>
Django
Reporter: srkunze | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: master
(models, ORM) |
Keywords: | Triage Stage: Ready for
| checkin
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Tim Graham <timograham@…>):
* status: new => closed
* resolution: => fixed
Comment:
In [changeset:"c002a0d39f18694f5e8a07d86684fc793b063056" c002a0d3]:
{{{
#!CommitTicketReference repository=""
revision="c002a0d39f18694f5e8a07d86684fc793b063056"
Fixed #26517 -- Fixed ExpressionWrapper with empty queryset.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/26517#comment:9>