django通过in查询符合数组中每一项的结果，也可以化简manytomany关系中的复杂查询

in¶

In a given iterable; often a list, tuple, or queryset.

Example:

Entry.objects.filter(id__in=[1, 3, 4])

SQL equivalent:

SELECT ... WHERE id IN (1, 3, 4);

You can also use a queryset to dynamically evaluate the list of valuesinstead of providing a list of literal values:

inner_qs = Blog.objects.filter(name__contains='Cheddar')
entries = Entry.objects.filter(blog__in=inner_qs)

This queryset will be evaluated as subselect statement:

SELECT ... WHERE blog.id IN (SELECT id FROM ... WHERE NAME LIKE '%Cheddar%')

If you pass in a QuerySet resulting from values() or values_list()as the value to an __in lookup, you need to ensure you are only extractingone field in the result. For example, this will work (filtering on the blognames):

inner_qs = Blog.objects.filter(name__contains='Ch').values('name')
entries = Entry.objects.filter(blog__name__in=inner_qs)

# 过滤投诉点（poi）所属的县区
if 'boroughs[]' in request.POST:
    boroughs = request.POST.getlist('boroughs[]')  # 注意boroughs[]的[]不能少
    if boroughs:
        # 先通过多对多关系的表，查出符合的关系
        relation_set = ComplaintRelatedAmapPois.objects.filter(order=1).filter(poi__adname_id__in=boroughs)
        # 在通过__in，查找记录结果集中符合关系结果集的数据
        record_set = record_set.filter(complaintri__complaintrelatedamappois__in=relation_set)

filter(poi__adname_id__in=boroughs)

boroughs是通过post传递过来的数组，内容是区县的id，这里使用in表示条件符合boroughs数组中的id的数据

重点在第二条：

record_set.filter(complaintri__complaintrelatedamappois__in=relation_set)

因为Poi与ComplaintRI是manytomany的关系，Record是ComplaintRI的外键：

# 分析并记录每条投诉的地址，经纬度，相关站点
class ComplaintRI(models.Model):
    complaint = models.ForeignKey(Record, on_delete=models.CASCADE, default=None, null=True)
    wherestr = models.ForeignKey(RecordLocation, on_delete=models.CASCADE, default=None, null=True)
    where = models.ManyToManyField(Poi, through='ComplaintRelatedAmapPois', through_fields=('complaint', 'poi'))
    # whenstr = models.CharField(max_length=100, default=None, null=True)
    when = models.DateTimeField(null=True)
    phone = models.ForeignKey(CustomerPhoneNumber, on_delete=models.CASCADE, default=None, null=True)
    # lnglat = models.ForeignKey(ComplaintLngLat, on_delete=models.CASCADE, default=None, null=True)
    servicetype = models.ForeignKey(Device, on_delete=models.CASCADE, default=None, null=True)

而且这个manytomany关系有额外信息，记录在ComplaintRelatedAmapPois表中：

# 通过投诉点地址搜索到的高德地图的点，因为搜索结果可能有多个，需要记录顺序order,因为顺序靠前的比较准
class ComplaintRelatedAmapPois(models.Model):
    poi = models.ForeignKey(Poi, on_delete=models.CASCADE, default=None)
    complaint = models.ForeignKey(ComplaintRI, on_delete=models.CASCADE, default=None)
    order = models.IntegerField(default=0)

需要先过滤出order=1的记录，再在这些记录中找Poi的区县符合post过来的id数组，但是得出的结果是ComplaintRelatedAmapPois结果集，我想跟Record对象合并查找条件，但是发现会遇到查询条件的歧义，详见（https://blog.csdn.net/qq_27361945/article/details/79611933）。不如分成两条查询，通过in实现，逻辑清晰。

        # 先通过多对多关系的表，查出符合的关系
        relation_set = ComplaintRelatedAmapPois.objects.filter(order=1).filter(poi__adname_id__in=boroughs)
        # 在通过__in，查找记录结果集中符合关系结果集的数据
        record_set = record_set.filter(complaintri__complaintrelatedamappois__in=relation_set)