从mongo BD中的facet命令获取信息

Question

我正在尝试从管道中提取名称列表，其中我得到以下内容：

 command_5 = {"$facet": {
        "list_of_station_names": my_query_1}}

并得到结果：

list_of_station_names  :  [{'desc': 'Sip Ave'}, {'desc': 'Vesey Pl &; River Terrace'}, {'desc': 'Murray St &; West St'},{'desc': 'E 81 St &; York Ave'}] 

但我需要列表中的结果不带属性名称“desc”，如下所示：

 list_of_station_names  :  ['Sip Ave', 'Vesey Pl &; River Terrace','Murray St &; West St','E 81 St &; York Ave']

Answer 1

您只能在刻面之后映射它。

db.collection.aggregate([
  {
    $facet: {
      list_of_station_names: []
    }
  },
  {
    $set: {
      list_of_station_names: {
        $map: {
          input: "$list_of_station_names",
          as: "n",
          in: "$n.desc"
        }
      }
    }
  }
])

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