Django mongo db筛选器查询未返回任何数据

Question

当我尝试om = OttMessage.objects.filter()时，它会返回ott_message集合中的所有文档。

但是当我尝试om = OttMessage.objects.filter(prediction_status = -1)时，它不返回任何数据。

OttMessage model.py相关行

prediction_status = IntField(default=-1, db_field='ps') 例如

ott_message集合中有很多文档的“ prediction_status”字段为-1

  {
     "classification" : null,
     "message_from" : "XXXXXXXX",
     "id" : "5b61d4649cdae332bf9151f9",
     "is_classified" : false,
     "prediction_status" : -1,
     "post_disposition" : null,
     "message" : "XXXXXXXXXXXXXXXXXXXXXX",
     "channel" : 1,
     "message_date" : "2018-08-01T15:42:30",
     "group_name" : "Resale Gurgaon req IC",
     "req_disposition" : null,
     "manual_tagged_status" : -1
  },
  {
     "prediction_status" : -1,
     "is_classified" : false,
     "classification" : null,
     "message_from" : "XXXXXXXXXXXXX",
     "id" : "5b61da629cdae343169150cf",
     "manual_tagged_status" : -1,
     "req_disposition" : null,
     "message" : "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
     "post_disposition" : null,
     "message_date" : "2018-08-01T15:50:19",
     "group_name" : "XXXXXXXXXXXXXXX",
     "channel" : 1
  }

有人能告诉我哪里出了问题吗？谢谢