Question

根据此处的Django文档：https://docs.djangoproject.com/en/2.1/ref/models/expressions/#using-f-with-annotations

我可以使用ExpressionWrapper进行日期计算。我试图这样使用它：

    sprints = Sprint.objects.annotate(
        duration=models.Case(
            models.When(
                Q(started__isnull=False) &
                Q(done__isnull=False),
                then=models.Value(
                    models.ExpressionWrapper(
                        (models.F('done') - models.F('started')),
                        output_field=models.DateTimeField()
                    ))
            ),
            models.When(
                Q(started__isnull=False) &
                Q(done__isnull=True),
                then=models.Value(
                    models.ExpressionWrapper(
                        (Now() - models.F('started')),
                        output_field=models.DateTimeField(),
                    ))
            ),
            output_field=models.DateTimeField()
        )).values_list('name',
                       'planned',
                       'started',
                       'done',
                       'duration')

但是从pytz尝试在ExpressionWrapper上进行自动定位时出现错误：

Traceback (most recent call last):
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/rest_framework/viewsets.py", line 103, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/rest_framework/views.py", line 483, in dispatch
    response = self.handle_exception(exc)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/rest_framework/views.py", line 443, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/rest_framework/views.py", line 480, in dispatch
    response = handler(request, *args, **kwargs)
  File "/home/phirt/src/core3/src/backend/portal/views/api/transformation.py", line 766, in get_sprint_data_csv
    for sprint in sprints:
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/db/models/query.py", line 272, in __iter__
    self._fetch_all()
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/db/models/query.py", line 1179, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1011, in apply_converters
    value = converter(value, expression, connection)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/db/backends/mysql/operations.py", line 247, in convert_datetimefield_value
    value = timezone.make_aware(value, self.connection.timezone)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/django/utils/timezone.py", line 269, in make_aware
    return timezone.localize(value, is_dst=is_dst)
  File "/home/phirt/local/venv/core3/lib/python3.6/site-packages/pytz/__init__.py", line 226, in localize
    if dt.tzinfo is not None:
AttributeError: 'str' object has no attribute 'tzinfo'

实际上，以pytz传递给dt的{{1}}参数是一个字符串，它正是我的ExpressionWrapper表达式：localize

我该如何做？

编辑：这是sprint模型：

ExpressionWrapper(F(done) - F(started))

Answer 1

我通过将查询注释更改为以下内容来使其工作：

B.temptable

Django ORM DateTimeField ExpressionWrapper QuerySet批注

1 个答案: