如何通过common _id字段过滤我的事件数组？

Question

我有这样的输出，但我想通过_id's过滤事件数组，这与父对象_id相同。我想根据这个条件过滤它。

[
    {
        "_id": "5cc45eb430aaba3cdc045dc0" ,
        "word": "Pasta",
        "translate": "Makarna",
        "kind": "İsim",
        "exampleSentence": "asljdalsd",
        "__v": 0,
        "events": [
            {
                "_id": "5cc45eb430aaba3cdc045dc0",
                "createdAt": "2019-04-27T13:52:15.721Z",
                "TenMinutesLater": "2019-04-27T13:52:25.721Z",
                "OneWeekLater": "2019-05-04T13:52:15.721Z",
                "OneMonthLater": "2019-05-27T13:52:15.721Z",
                "FourMonthLater": "2019-08-27T13:52:15.721Z",
                "__v": 0
            },
            {
                "_id": "5cc45ee630aaba3cdc045dc1",
                "createdAt": "2019-04-27T13:52:15.721Z",
                "TenMinutesLater": "2019-04-27T13:52:25.721Z",
                "OneWeekLater": "2019-05-04T13:52:15.721Z",
                "OneMonthLater": "2019-05-27T13:52:15.721Z",
                "FourMonthLater": "2019-08-27T13:52:15.721Z",
                "__v": 0
            }
        ]
    }
]

我想过滤我的事件数组，它与父对象_id具有相同的_id属性。我应该根据我想要的查询？

这是我的疑问

Word.find({ _id: req.params.id }, (err, words) => {
    if (err) {
      console.log(err);
    }
    const uid = words.map(word => word._id);
    console.log(req.params.id);
    Word.aggregate([
      {
        $match: {
          _id: {
            $in: uid.map(function(id) {
              return new mongoose.Types.ObjectId(id);
            })
          }
        }
      },
      {
        $lookup: {
          from: "tests",
          localField: "eventId",
          foreignField: "_id.str",
          as: "events"
        }
      }
    ])
      .then(data => {
        res.json(data);
      })
      .catch(err => {
        throw err;
      });
  });

我希望输出像这样。我如何用父对象的_id过滤它？

[
    {
        "_id": "5cc45eb430aaba3cdc045dc0" ,
        "word": "Pasta",
        "translate": "Makarna",
        "kind": "İsim",
        "exampleSentence": "asljdalsd",
        "__v": 0,
        "events": [
            {
                "_id": "5cc45eb430aaba3cdc045dc0",
                "createdAt": "2019-04-27T13:52:15.721Z",
                "TenMinutesLater": "2019-04-27T13:52:25.721Z",
                "OneWeekLater": "2019-05-04T13:52:15.721Z",
                "OneMonthLater": "2019-05-27T13:52:15.721Z",
                "FourMonthLater": "2019-08-27T13:52:15.721Z",
                "__v": 0
        ]
    }
]

Answer 1

这里$ lookup将返回与您可能已经知道的匹配localfield / foreign字段条件的所有事件。 如果要按其他条件筛选结果（从描述中不是很清楚），可以在联合集合中使用管道功能（在3.6中引入）。 $ lookup中的示例管道（从官方站点获取）看起来像这样。 因此，您可以看到您可以对已加入的集合执行匹配并过滤您的事件。

db.orders.aggregate([
   {
      $lookup:
         {
           from: "warehous`enter code here`es",
           let: { order_item: "$item", order_qty: "$ordered" },
           pipeline: [
              { $match:
                 { $expr:
                    { $and:
                       [
                         { $eq: [ "$stock_item",  "$$order_item" ] },
                         { $gte: [ "$instock", "$$order_qty" ] }
                       ]
                    }
                 }
              },
              { $project: { stock_item: 0, _id: 0 } }
           ],
           as: "stockdata"
         }
    }
])

Answer 2

谢谢你的回答，但我终于解决了这个问题。它工作得很好

Word.find({ _id: req.params.id }, (err, words) => {
    if (err) {
      console.log(err);
    }
    const uid = words.map(word => word._id);
    Word.aggregate([
      {
        $match: {
          _id: {
            $in: uid.map(function(id) {
              return mongoose.Types.ObjectId(id);
            })
          }
        }
      },
      {
        $lookup: {
          from: "tests",
          localField: "_id.str",
          foreignField: "eventId",
          as: "events"
        }
      },
      {
        $addFields: {
          events: {
            $filter: {
              input: "$events",
              as: "event",
              cond: {
                $eq: ["$$event._id", mongoose.Types.ObjectId(req.params.id)]
              }
            }
          }
        }
      }
    ])
      .then(data => {
        res.json(data);
      })
      .catch(err => {
        throw err;
      });
  });