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我在 Django 视图中这样做：

def by_gear(gear):
    types = {
        'imaging_telescopes': Telescope,
        'guiding_telescopes': Telescope,
        'mounts': Mount,
        'imaging_cameras': Camera,
        'guiding_cameras': Camera,
        'focal_reducers': FocalReducer,
        'software': Software,
        'filters': Filter,
        'accessories': Accessory,
    }
    filters = reduce(operator.or_, [Q(**{'%s__gear_ptr__pk' % t: gear.pk}) for t in types])
    images = Image.objects.filter(filters).distinct()

    return images

那是因为我有一个装备，但我不知道它是什么装备（望远镜、相机等）。这是一个基本模型。

所以我用它来判断所有的可能性reduce。由于 Gear 的所有子类（也是 Django 模型）都pk与基类 Gear 共享，我可以这样做。我知道它的可读性不是很好，我也没有解释得太清楚，但是如果你看一下下面生成的 SQL，就会清楚。

我正在尝试获取使用该设备（Gear）拍摄的所有图像，因此请查看它pk是否在image__telescopes、image__imaging_cameras等中。

然而，这最终产生了这个 SQL：

SELECT COUNT(DISTINCT "astrobin_image"."id") FROM "astrobin_image"

LEFT OUTER JOIN "astrobin_image_imaging_telescopes"
ON ("astrobin_image"."id" = "astrobin_image_imaging_telescopes"."image_id")

LEFT OUTER JOIN "astrobin_image_guiding_telescopes"
ON ("astrobin_image"."id" = "astrobin_image_guiding_telescopes"."image_id")

LEFT OUTER JOIN "astrobin_image_software"
ON ("astrobin_image"."id" = "astrobin_image_software"."image_id")

LEFT OUTER JOIN "astrobin_image_filters"
ON ("astrobin_image"."id" = "astrobin_image_filters"."image_id")

LEFT OUTER JOIN "astrobin_image_imaging_cameras"
ON ("astrobin_image"."id" = "astrobin_image_imaging_cameras"."image_id")

LEFT OUTER JOIN "astrobin_image_mounts"
ON ("astrobin_image"."id" = "astrobin_image_mounts"."image_id")

LEFT OUTER JOIN "astrobin_image_focal_reducers"
ON ("astrobin_image"."id" = "astrobin_image_focal_reducers"."image_id")

LEFT OUTER JOIN "astrobin_image_accessories"
ON ("astrobin_image"."id" = "astrobin_image_accessories"."image_id")

LEFT OUTER JOIN "astrobin_image_guiding_cameras"
ON ("astrobin_image"."id" = "astrobin_image_guiding_cameras"."image_id")

WHERE ("astrobin_image_imaging_telescopes"."telescope_id" = 4723
OR "astrobin_image_guiding_telescopes"."telescope_id" = 4723
OR "astrobin_image_software"."software_id" = 4723
OR "astrobin_image_filters"."filter_id" = 4723
OR "astrobin_image_imaging_cameras"."camera_id" = 4723
OR "astrobin_image_mounts"."mount_id" = 4723
OR "astrobin_image_focal_reducers"."focalreducer_id" = 4723
OR "astrobin_image_accessories"."accessory_id" = 4723
OR "astrobin_image_guiding_cameras"."camera_id" = 4723 )

所以这个查询需要 2 秒以上......你能建议一种方法来改善这个混乱吗？

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