#14336: list_display should be able to contain sortable references to extra
and/or
annotated fields
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Reporter: pmclanahan | Owner: nobody
Status: new | Milestone:
Component: django.contrib.admin | Version: 1.2
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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Overriding the `queryset` method of a `ModelAdmin` should be an easy way
to annotate the `QuerySet` used in the admin list view for a model. My use
case is that I have two `IntegerField`s containing counts of various
things, but what I'd like to be able to display and sort by in the admin
list view is the sum of these two fields. This can best be explained by an
example:
{{{
#!python
# Given this model
class Article(models.Model):
title = models.CharField(max_length=255)
num_a = models.PositiveIntegerField()
num_b = models.PositiveIntegerField()
# Want ModelAdmin like...
class ArticleAdmin(admin.ModelAdmin):
list_display = ('title' 'total_nums')
def queryset(self, request):
qs = super(ArticleAdmin, self).queryset(request)
return qs.extra(select={'total_nums':'num_a + num_b'})
}}}
This fails at model validation with a `ImproperlyConfigured` exception in
`django.contrib.admin.validation.validate` because the model has no
'total_nums' field, which we know. But the model validation mechanism has
no access to the instance of the `ModelAdmin`, and therefore no access to
the queryset to be able to check for any extras or annotations.
I tried fixing this and would have submitted a patch, but I failed in the
time I had. However, there is a workaround I discovered and am using, but
it seems silly. You change `ArticleAdmin` to the following:
{{{
#!python
class ArticleAdmin(admin.ModelAdmin):
list_display = ('title' 'total')
def total(self, obj):
return obj.total_nums
total.admin_order_field = 'total_nums'
def queryset(self, request):
qs = super(ArticleAdmin, self).queryset(request)
return qs.extra(select={'total_nums':'num_a + num_b'})
}}}
This seems overly verbose and a little hacky, but it does work. I'd say
that makes this ticket non-urgent, though I do wonder how many developers
gave up before discovering this technique.
--
Ticket URL: <http://code.djangoproject.com/ticket/14336>
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