Django，DRF：如何在原始 SQL 查询中使用分页？

Question

我想在 Django REST 框架的 ListAPIView 中使用以下原始查询。 我不确定如何使用原始 SQL 查询而不是查询集来支持分页。 我已经研究过了，并没有发现很多对我有意义的东西。

如果我想使用查询集，它看起来像这样 如果我想使用原始 SQL 查询，该怎么做？

class VideoListView(generics.ListAPIView):
    queryset = Video.objects.raw(...)
    serializer_class = VideoSerializer

SELECT DISTINCT "t"."id",
                "t"."title",
                "t"."thumbnail_url",
                "t"."preview_url",
                "t"."embed_url",
                "t"."duration",
                "t"."views",
                "t"."is_public",
                "t"."published_at",
                "t"."created_at",
                "t"."updated_at",
                EXISTS
  (SELECT (1) AS "a"
   FROM "videos_history" U0
   WHERE (U0."user_id" IS NULL
          AND U0."video_id" = "t"."id")
   LIMIT 1) AS "is_viewed",
                EXISTS
  (SELECT (1) AS "a"
   FROM "videos_favorite" U0
   WHERE (U0."user_id" IS NULL
          AND U0."video_id" = "t"."id")
   LIMIT 1) AS "is_favorited",
                EXISTS
  (SELECT (1) AS "a"
   FROM "videos_track" U0
   INNER JOIN "videos_playlist" U1 ON (U0."playlist_id" = U1."id")
   WHERE (U1."is_wl"
          AND U1."user_id" IS NULL
          AND U0."video_id" = "t"."id")
   LIMIT 1) AS "is_wl"
FROM (
  (SELECT "videos_video".*
   FROM "videos_video"
   WHERE ("videos_video"."is_public"
      AND "videos_video"."published_at" <= '2022-01-03 05:20:16.725884+00:00'
      AND "videos_video"."title" LIKE '%word')
   ORDER BY "videos_video"."published_at" DESC
   LIMIT 20)
UNION
  (SELECT "videos_video".*
   FROM "videos_video"
   LEFT OUTER JOIN "videos_video_tags" ON ("videos_video"."id" = "videos_video_tags"."video_id")
   LEFT OUTER JOIN "videos_tag" ON ("videos_video_tags"."tag_id" = "videos_tag"."id")
   WHERE ("videos_video"."is_public"
      AND "videos_video"."published_at" <= '2022-01-03 05:20:16.725884+00:00'
      AND "videos_tag"."name" LIKE '%word')
   ORDER BY "videos_video"."published_at" DESC
   LIMIT 20)
) AS t
ORDER BY "t"."published_at" DESC
LIMIT 20;

我需要创建一个自定义分页器还是什么？我更加困惑，因为我正在使用 LIMIT 和其他方法进行子查询。

--- 添加models.py等... ---

# models.py
class Tag(models.Model):
    name = models.CharField(unique=True, max_length=30)
    created_at = models.DateTimeField(default=timezone.now)
    ...


class Video(models.Model):
    title = models.CharField(max_length=300)
    tags = models.ManyToManyField(Tag, blank=True)
    updated_at = models.DateTimeField(auto_now=True)
    ...


class History(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    video = models.ForeignKey(Video, on_delete=models.CASCADE)
    ...


class Favorite(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE
    video = models.ForeignKey(Video, on_delete=models.CASCADE)
    ...


class Playlist(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    is_wl = models.BooleanField(default=False, editable=False)
    ...


class Track(models.Model):
    playlist = models.ForeignKey(Playlist, on_delete=models.CASCADE, null=True)
    video = models.ForeignKey(Video, on_delete=models.CASCADE)
    ...

最初使用的慢查询集和 SQL 查询。

Video.objects.annotate(
    is_viewed=Exists(History.objects.filter(user=user, video=OuterRef("pk"))),
    is_favorited=Exists(
        Favorite.objects.filter(user=user, video=OuterRef("pk"))
    ),
    is_wl=Exists(
        Track.objects.filter(
            playlist__user=user, playlist__is_wl=True, video=OuterRef("pk")
        )
    ),
).filter(
    Q(title__contains=value)
    | Q(tags__name__contains=value)),
    is_public=True,
    published_at__lte=timezone.now(),
).order_by("-published_at").distinct()

SELECT DISTINCT "videos_video"."id",
                "videos_video"."published_at",
                EXISTS
  (SELECT (1) AS "a"
   FROM "videos_history" U0
   WHERE (U0."user_id" IS NULL
          AND U0."video_id" = "videos_video"."id")
   LIMIT 1) AS "is_viewed",
                EXISTS
  (SELECT (1) AS "a"
   FROM "videos_favorite" U0
   WHERE (U0."user_id" IS NULL
          AND U0."video_id" = "videos_video"."id")
   LIMIT 1) AS "is_favorited",
                EXISTS
  (SELECT (1) AS "a"
   FROM "videos_track" U0
   INNER JOIN "videos_playlist" U1 ON (U0."playlist_id" = U1."id")
   WHERE (U1."is_wl"
          AND U1."user_id" IS NULL
          AND U0."video_id" = "videos_video"."id")
   LIMIT 1) AS "is_wl"
FROM "videos_video"
LEFT OUTER JOIN "videos_video_tags" ON ("videos_video"."id" = "videos_video_tags"."video_id")
WHERE ("videos_video"."is_public"
       AND "videos_video"."published_at" <= '2021-12-27 13:34:29.103369+00:00'
       AND ("videos_video"."title" &@~ 'word'
            OR "videos_video_tags"."tag_id" IN
              (SELECT U0."id"
               FROM "videos_tag" U0
               WHERE U0."name" &@~ 'word')))
ORDER BY "videos_video"."published_at" DESC
LIMIT 20;

Answer 1

如果您从rest_framework.pagination 询问通用PageNumberPagination，通常是这样完成的。您使用默认值创建自己的分页类：

class VideoPagination(PageNumberPagination):
    max_page_size = 100
    page_size_query_param = 'page_size'
    page_size = 25

然后你只需将它添加到你的视图中：

class VideoListView(generics.ListAPIView):
    queryset = Video.objects.all()
    serializer_class = VideoSerializer
    pagination_class = VideoPagination

就是这样，你可以使用参数page和page_size。