Firebase - 基于时间戳的OrderByChild

Question

我有以下数据结构，我想按upload_on排序，其中最新的时间戳首先出现：

#Function that recursively extracts values out of the object into a flattened dictionary
def flatten_json(data):
    flat = [] #list of flat dictionaries
    def flatten(y):
        out = {}

        def flatten2(x, name=''):
            if type(x) is dict:
                for a in x:
                    if a == "name": 
                            flatten2(x["value"], name + x[a] + '_')
                    else:  
                        flatten2(x[a], name + a + '_')
            elif type(x) is list:
                for a in x:
                    flatten2(a, name + '_')
            else:
                out[name[:-1]] = x

        flatten2(y)
        return out

#Loop needed to flatten multiple objects
    for i in range(len(data)):
        flat.append(flatten(data[i]).copy())

    return json_normalize(flat) 

我有以下代码来检索数据并对其进行排序：

"hd2CnPPZ5FMKjpzFJNUc4xVLVUW2" : {
  "media" : {
    "-KJkxpnRg_2ZK4tEjGBN" : {
      "uploaded_on" : 1465405365513,
      "url" : "<my-firebase-storage-url>"
    },

但是，我的商品没有正确订购，最旧的时间戳首先出现。我尝试了在uploaded_on的前面放一个减号，但这没有任何区别。

我做错了什么指针？