Question

我按特定顺序拥有ID

>>> album_ids = [24, 15, 25, 19, 11, 26, 27, 28]
>>> albums = Album.objects.filter( id__in=album_ids, published= True )
>>> [album.id for album in albums]
[25, 24, 27, 28, 26, 11, 15, 19]

我需要在queryset中将相册中的相册作为album_ids中的id。有人请告诉我如何维护订单？或者像在album_ids中那样获取专辑？

Answer 1

自从Djnago 1.8以来你可以这样做

from django.db.models import Case, When

pk_list = [10, 2, 1]
preserved = Case(*[When(pk=pk, then=pos) for pos, pk in enumerate(pk_list)])
queryset = MyModel.objects.filter(pk__in=pk_list).order_by(preserved)

Answer 2

假设ID列表不是太大，您可以将QS转换为列表并在Python中对其进行排序：

album_list = list(albums)
album_list.sort(key=lambda album: album_ids.index(album.id))

Answer 3

你不能通过ORM在django中做到这一点。但是你自己实现它很简单：

album_ids = [24, 15, 25, 19, 11, 26, 27, 28]
albums = Album.objects.filter(published=True).in_bulk(album_ids) # this gives us a dict by ID
sorted_albums = [albums[id] for id in albums_ids if id in albums]

Answer 4

您可以使用extra QuerySet修饰符

通过ORM在Django中执行此操作

open(content) {
  this.modalService.open(content).result.then((result) => {
    this.closeResult = `Closed with: ${result}`;
  }, (reason) => {
    this.closeResult = `Dismissed ${this.getDismissReason(reason)}`;
  });
}

Answer 5

使用@Soitje 的解决方案：https://stackoverflow.com/a/37648265/1031191

def filter__in_preserve(queryset: QuerySet, field: str, values: list) -> QuerySet:
    """
    .filter(field__in=values), preserves order.
    """
    # (There are not going to be missing cases, so default=len(values) is unnecessary)
    preserved = Case(*[When(**{field: val}, then=pos) for pos, val in enumerate(values)])
    return queryset.filter(**{f'{field}__in': values}).order_by(preserved)


album_ids = [24, 15, 25, 19, 11, 26, 27, 28]
albums =filter__in_preserve(album.objects, 'id', album_ids).all()

请注意，您需要确保专辑 ID 是唯一的。

备注：

1.) 此解决方案应该可以安全地与任何其他字段一起使用，而不会冒 sql 注入攻击的风险。

2.) Case (Django doc) 生成一个 sql 查询，如 https://stackoverflow.com/a/33753187/1031191

order by case id 
          when 24 then 0
          when 15 then 1
          ...
          else 8 
end

Answer 6

如果您使用MySQL，并希望通过使用字符串列来保留顺序。

words = ['I', 'am', 'a', 'human']
ordering = 'FIELD(`word`, %s)' % ','.join(str('%s') for word in words)
queryset = ModelObejectWord.objects.filter(word__in=tuple(words)).extra(
                            select={'ordering': ordering}, select_params=words, order_by=('ordering',))

django：__ in query lookup不保持querset中的顺序

6 个答案: