mongodb - MongoDB使用带有数组的DBref连接到对象

Question

您好，我正在尝试加入不同集合中的文档

$lookup: {
  from: 'operation',
  localField: 'operations._id',
  foreignField: '_id',
  as: 'string'
}

我尝试了一切，但没有任何效果，我希望通过 id 连接来进行所有操作。

这是我的第一份文件

这是我的第二份文件

Answer 1

你只需要更换

localField: 'operations._id'

和：

localField: 'operations.$id',

这是我尝试过的：

1. 插入一些操作：

    db.insert.Operation([
      {
        operationName: "test",
        data: [1, 2, 3],
      },
      {
        operationName: "xx",
        data: [4, 5, 6],
      },
      {
        operationName: "AA",
        data: [7, 8, 9],
      },
      {
        operationName: "CCC",
        data: [10, 11, 12],
      },
      {
        operationName: "PPP",
        data: [13, 14, 15],
      },
      {
        operationName: "IIII",
        data: [16, 17, 18],
      },
    ]);
   

2. 插入第一个文档，我调用了集合Employee：

    db.insert.Employee([
      {
        firstName: "chuck",
        ladtName: "Norris",
        enabled: true,
        operations: [
          {
            $ref: "Operations",
            $id: ObjectId("6044ebeede8ee738e720d3a5"),
          },
          {
            $ref: "Operations",
            $id: ObjectId("6044ebeede8ee738e720d3a6"),
          },
          {
            $ref: "Operations",
            $id: ObjectId("6044ebeede8ee738e720d3a8"),
          },
          {
            $ref: "Operations",
            $id: ObjectId("6044ebeede8ee738e720d3a9"),
          },
          {
            $ref: "Operations",
            $id: ObjectId("6044ebeede8ee738e720d3aa"),
          },
        ],
      },
    ]);
   

3. 我写了这个查询：

    db.Employee.aggregate([{
        $lookup:{
            from:"Operation",
            localField:"operations.$id",
            foreignField:"_id",
            as:"Result"
        }
    }])
   

这就是它的全部。

结果如下：

{ 
    "_id" : ObjectId("6044eee6de8ee738e720d3ab"), 
    "firstName" : "chuck", 
    "ladtName" : "Norris", 
    "enabled" : true, 
    "operations" : [
        DBRef("Operations", ObjectId("6044ebeede8ee738e720d3a5")), 
        DBRef("Operations", ObjectId("6044ebeede8ee738e720d3a6")), 
        DBRef("Operations", ObjectId("6044ebeede8ee738e720d3a8")), 
        DBRef("Operations", ObjectId("6044ebeede8ee738e720d3a9")), 
        DBRef("Operations", ObjectId("6044ebeede8ee738e720d3aa"))
    ], 
    "Result" : [
        {
            "_id" : ObjectId("6044ebeede8ee738e720d3a5"), 
            "operationName" : "test", 
            "data" : [
                1.0, 
                2.0, 
                3.0
            ]
        }, 
        {
            "_id" : ObjectId("6044ebeede8ee738e720d3a6"), 
            "operationName" : "xx", 
            "data" : [
                4.0, 
                5.0, 
                6.0
            ]
        }, 
        {
            "_id" : ObjectId("6044ebeede8ee738e720d3a8"), 
            "operationName" : "CCC", 
            "data" : [
                10.0, 
                11.0, 
                12.0
            ]
        }, 
        {
            "_id" : ObjectId("6044ebeede8ee738e720d3a9"), 
            "operationName" : "PPP", 
            "data" : [
                13.0, 
                14.0, 
                15.0
            ]
        }, 
        {
            "_id" : ObjectId("6044ebeede8ee738e720d3aa"), 
            "operationName" : "IIII", 
            "data" : [
                16.0, 
                17.0, 
                18.0
            ]
        }
    ]
}