Django ModelAdmin get_object 优化

Question

我在Django ModelAdmin 列表视图中优化了get_queryset：

• .only('field1', 'field2',)
• .select_related('rel1',)

这些优化与 get_object 更改视图所需的不同：

• .only('field1', 'field2', 'field3',)
• .select_related('rel1__rel2', 'rel3',)
• .prefetch_related(...)

事情是，get_queryset and get_object are coupled:

class BaseModelAdmin(...):

  ...

  def get_object(self, request, object_id, from_field=None):
      """
      Returns an instance matching the field and value provided, the primary
      key is used if no field is provided. Returns ``None`` if no match is
      found or the object_id fails validation.
      """
      queryset = self.get_queryset(request)
      model = queryset.model
      field = model._meta.pk if from_field is None else model._meta.get_field(from_field)
      try:
          object_id = field.to_python(object_id)
          return queryset.get(**{field.name: object_id})
      except (model.DoesNotExist, ValidationError, ValueError):
          return None

我怎样才能覆盖get_queryset 而不必复制/粘贴上面的所有样板？

Answer 1

我想出了这个解决方案，这似乎是一个不错的折衷方案：

def get_queryset(self, request):
    queryset = super().get_queryset(request)
    if request.resolver_match.url_name.endswith('_change'):
        # admin change view
        queryset = queryset.only(
            'iso_code',
            *get_translation_fields('name'),
            'official_languages',
            'active',
            'currency_code',
            'currency_symbol',
        )
    else:
        # admin change list
        queryset = queryset.only(
            'iso_code',
            'name',
            'active',
        )
    return queryset

Answer 2

您的用例不是很常见，所以我认为没有任何明智的方法可以在不重写get_object 的情况下实现您的需求。我会这样做：

# A parameter with default False value shouldn't screw things up
def get_queryset(request, for_object=False):
    qs = super(YourModelAdmin, self).get_queryset(request)
    if for_object:
        qs = qs.select_related('rel1__rel2', 'rel3')
        qs = .prefetch_related('rel4', 'rel5')
        return qs.only('field1', 'field2', 'field3')
    else:
        qs = qs.select_related('rel1')
        return qs.only('field1', 'field2')

def get_object(self, request, object_id, from_field=None):
    # Don't forget to add new param here
    queryset = self.get_queryset_for_object(request, for_object=True)
    model = queryset.model
    field = model._meta.pk if from_field is None else model._meta.get_field(from_field)
    try:
        object_id = field.to_python(object_id)
        return queryset.get(**{field.name: object_id})
    except (model.DoesNotExist, ValidationError, ValueError):
        return None