node.js - 发送 MongoDB 数组以从 MongoDB 中的不同集合获取结果

Question

我有一个包含考勤卡的 MongoDB 集合。我有第二个包含位置的集合。通常，如果我正在寻找当时值类的人，我会这样做(每次登录都必须注销):

TimeCard.aggregate([
    { $match: {agency_id: req.query.agency_id}},
    { $sort: { user_id: 1, received_time: -1 }},
    { $group: { _id: "$user_id", count_types: { $sum: 1 }, lastTime: { $last: "$received_time" }}},
    { $match: { count_types: { $mod: [2, 1] }}},
    { $lookup: { from: "locations", localField: "_id", foreignField: "user_id", as: "Test" }}
], function(err, docs){
        if(err){console.log(err);}
        else {res.json(docs);}
    });

这会给我这个结果:

 [
   {
    "_id": "123-88",
    "count_types": 5,
    "lastTime": "2017-04-20T01:30:18.713Z",
    "Test": [
      {
        "_id": "58fa4021ffa99100116585e0",
        "user_id": "123-88",
        "agency_id": "44",
        "contract_region_id": "contract-region-id-007",
        "department_id": "department-id-42",
        "shift_id": "shift-id-45",
        "unit_id": "unit-id-88",
        "received_time": "2017-04-21T17:23:45.672Z",
        "location": "Science Lab",
        "__v": 0
      },
      {
        "_id": "58fed3efdac1bd00112a914b",
        "user_id": "123-88",
        "agency_id": "44",
        "contract_region_id": "contract-region-id-007",
        "department_id": "department-id-42",
        "shift_id": "shift-id-45",
        "unit_id": "unit-id-88",
        "received_time": "2017-04-25T04:43:27.501Z",
        "location": "Gym",
        "__v": 0
      }
    ]
  }
]

现在我可以在数组中拥有多个用户，并且每个用户都有自己的位置数据。我想要的只是他们所在的最后一个位置(基于测试数组中的 receive_time )。所以我最好的猜测是，我需要首先获取 user_ids 列表，然后调用第二个集合并传入数组以获取结果，但我不确定如何正确执行此操作，或者这是否是最好的方法去做这个。再次感谢您的帮助。

Answer 1

使用$filter 运算符获取 Test 数组中 received_time 键与聚合 lastTime 字段匹配的唯一元素。您可以在 $addFields 中应用此功能 如果您的 MongoDB Server 版本是 3.4 或更高版本，则管道步骤:

TimeCard.aggregate([
    { $match: {agency_id: req.query.agency_id}},
    { $sort: { user_id: 1, received_time: -1 }},
    { $group: { _id: "$user_id", count_types: { $sum: 1 }, lastTime: { $last: "$received_time" }}},
    { $match: { count_types: { $mod: [2, 1] }}},
    { $lookup: { from: "locations", localField: "_id", foreignField: "user_id", as: "Test" }},
    {
        $addFields: {
            Test: {
                $filter: {
                    input: "$Test",
                    as: "user",
                    cond: { $eq: ["$lastTime", "$$user.received_time"] }
                }
            }
        }
    }
], function(err, docs){
    if(err){console.log(err);}
    else {res.json(docs);}
});

<小时/>

如果您的 MongoDB 服务器不支持 $addFields 然后使用 $project 管道:

TimeCard.aggregate([
    { $match: {agency_id: req.query.agency_id}},
    { $sort: { user_id: 1, received_time: -1 }},
    { $group: { _id: "$user_id", count_types: { $sum: 1 }, lastTime: { $last: "$received_time" }}},
    { $match: { count_types: { $mod: [2, 1] }}},
    { $lookup: { from: "locations", localField: "_id", foreignField: "user_id", as: "Test" }},
    {
        $project: {
            count_types: 1,
            lastTime: 1,
            Test: {
                $filter: {
                    input: "$Test",
                    as: "user",
                    cond: { $eq: ["$lastTime", "$$user.received_time"] }
                }
            }
        }
    }
], function(err, docs){
    if(err){console.log(err);}
    else {res.json(docs);}
});