{{{
class State(models.Model):
pass
class County(models.Model):
name = CharField(max_length=50)
state = ForeignKey(State, related_name='counties')
}}}
I can execute the following query just fine:
{{{
County.objects.filter(
Exists(State.objects.filter(counties=OuterRef('pk'), name="Texas")),
name="Dallas",
)
}}}
But a similar query using When does not work:
{{{
>>> County.objects.annotate(
status=Case(
When(Exists(State.objects.filter(counties=OuterRef('pk'),
name="Texas")), name="Dallas", then=Value("DALLAS COUNTY")),
default=Value("ELSEWHERE"),
))
}}}
Instead the arguments must be wrapped in a Q object:
{{{
>>> County.objects.annotate(
status=Case(
When(Q(Exists(State.objects.filter(counties=OuterRef('pk'),
name="Texas")), name="Dallas"), then=Value("DALLAS COUNTY")),
default=Value("ELSEWHERE"),
))
}}}
This is inconvenient and inconsistent with how filter works, as shown.
When's __init__ method can be modified to allow similar input as filter.
[https://github.com/rheard/django/commit/978e796bb18414d995d515ab7923831149300977
Code is in a branch in my repo], but as this is my first time contributing
to Django, I want to make sure I open a ticket and get feedback first.
--
Ticket URL: <https://code.djangoproject.com/ticket/31606>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Old description:
New description:
I don't seem to be able to provide an Exists expression to When alongside
keyword arguments like you can with filter. For instance, consider:
{{{
class State(models.Model):
pass
class County(models.Model):
name = CharField(max_length=50)
state = ForeignKey(State, related_name='counties')
}}}
I can execute the following query just fine:
{{{
County.objects.filter(
Exists(State.objects.filter(counties=OuterRef('pk'), name="Texas")),
name="Dallas",
)
}}}
But a similar query using When does not work:
{{{
>>> County.objects.annotate(
status=Case(
When(Exists(State.objects.filter(counties=OuterRef('pk'),
name="Texas")), name="Dallas", then=Value("DALLAS COUNTY")),
default=Value("ELSEWHERE"),
))
TypeError: When() supports a Q object, a boolean expression, or lookups as
a condition.
}}}
Instead the arguments must be wrapped in a Q object:
{{{
>>> County.objects.annotate(
status=Case(
When(Q(Exists(State.objects.filter(counties=OuterRef('pk'),
name="Texas")), name="Dallas"), then=Value("DALLAS COUNTY")),
default=Value("ELSEWHERE"),
))
}}}
This is inconvenient and inconsistent with how filter works, as shown.
When's __init__ method can be modified to allow similar input as filter.
[https://github.com/rheard/django/commit/978e796bb18414d995d515ab7923831149300977
Code is in a branch in my repo], but as this is my first time contributing
to Django, I want to make sure I open a ticket and get feedback first.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:1>
Old description:
> I don't seem to be able to provide an Exists expression to When alongside
> keyword arguments like you can with filter. For instance, consider:
>
> {{{
> class State(models.Model):
> pass
>
> class County(models.Model):
> name = CharField(max_length=50)
> state = ForeignKey(State, related_name='counties')
> }}}
>
> I can execute the following query just fine:
>
> {{{
> County.objects.filter(
> Exists(State.objects.filter(counties=OuterRef('pk'), name="Texas")),
> name="Dallas",
> )
> }}}
>
> But a similar query using When does not work:
>
> {{{
> >>> County.objects.annotate(
> status=Case(
> When(Exists(State.objects.filter(counties=OuterRef('pk'),
> name="Texas")), name="Dallas", then=Value("DALLAS COUNTY")),
> default=Value("ELSEWHERE"),
> ))
> TypeError: When() supports a Q object, a boolean expression, or lookups
> as a condition.
> }}}
>
> Instead the arguments must be wrapped in a Q object:
>
> {{{
> >>> County.objects.annotate(
> status=Case(
> When(Q(Exists(State.objects.filter(counties=OuterRef('pk'),
> name="Texas")), name="Dallas"), then=Value("DALLAS COUNTY")),
> default=Value("ELSEWHERE"),
> ))
> }}}
>
> This is inconvenient and inconsistent with how filter works, as shown.
>
> When's __init__ method can be modified to allow similar input as filter.
> [https://github.com/rheard/django/commit/978e796bb18414d995d515ab7923831149300977
> Code is in a branch in my repo], but as this is my first time
> contributing to Django, I want to make sure I open a ticket and get
> feedback first.
New description:
I don't seem to be able to provide an Exists expression to When alongside
keyword arguments like you can with filter. For instance, consider:
{{{
class State(models.Model):
pass
class County(models.Model):
name = CharField(max_length=50)
state = ForeignKey(State, related_name='counties')
}}}
I can execute the following query just fine:
{{{
County.objects.filter(
Exists(State.objects.filter(counties=OuterRef('pk'), name="Texas")),
name="Dallas",
)
}}}
But a similar query using When does not work:
{{{
>>> County.objects.annotate(
status=Case(
When(Exists(State.objects.filter(counties=OuterRef('pk'),
name="Texas")), name="Dallas", then=Value("DALLAS COUNTY")),
default=Value("ELSEWHERE"),
))
TypeError: When() supports a Q object, a boolean expression, or lookups as
a condition.
}}}
Instead the arguments must be wrapped in a Q object:
{{{
>>> County.objects.annotate(
status=Case(
When(Q(Exists(State.objects.filter(counties=OuterRef('pk'),
name="Texas")), name="Dallas"), then=Value("DALLAS COUNTY")),
default=Value("ELSEWHERE"),
))
}}}
This is inconvenient and inconsistent with how filter works, as shown.
When's __init__ method can be modified to allow similar input as filter.
[https://github.com/rheard/django/commit/978e796bb18414d995d515ab7923831149300977
Code is in a branch in my repo], but as this is my first time contributing
to Django, I want to make sure I open a ticket and get feedback first.
Also I wasn't sure how to classify this. I wasn't sure if it was a bug, as
I wasn't sure if it was designed this way.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:2>
* type: Cleanup/optimization => New feature
* version: 3.0 => master
* component: Uncategorized => Database layer (models, ORM)
* stage: Unreviewed => Accepted
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:3>
Comment (by felixxm):
[https://github.com/django/django/pull/12951 PR]
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:4>
* needs_docs: 0 => 1
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:5>
* owner: nobody => Ryan Heard
* needs_docs: 1 => 0
* status: new => assigned
* stage: Accepted => Ready for checkin
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:6>
* status: assigned => closed
* resolution: => fixed
Comment:
In [changeset:"587b179d4115f2e4dbc425d1ae035be9eb22197b" 587b179d]:
{{{
#!CommitTicketReference repository=""
revision="587b179d4115f2e4dbc425d1ae035be9eb22197b"
Fixed #31606 -- Allowed using condition with lookups in When() expression.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/31606#comment:7>