Mongodb 嵌套localField时的$lookup

MongoDB版本3.4.10（应用程序使用Meteor框架）

目标：在运行时根据需要将_id引用的文档聚合到包含文档中

我有

材料

，

模型

，和

目录

收藏，以及以下文档：

材料

 { "_id" : "cf4KgXw7ZK6ukdzR7", "name" : "parquet_wood_mahogany" }

{
  "_id" : "Mwp5eYYZ4GZzvZuoK",
  "name" : "top_square_chamfered",
  "type" : "top"
}
{
  "_id" : "CqhS2m2RcLZ2Bm4eb",
  "name" : "skirt_square",
  "type" : "skirt"
}
{
  "_id" : "dYP22ajALnWBwpBj2",
  "name" : "leg_square",
  "type" : "leg"
}

型号

 { "_id" : "cf4KgXw7ZK6ukdzR7", "name" : "parquet_wood_mahogany" }

{
  "_id" : "Mwp5eYYZ4GZzvZuoK",
  "name" : "top_square_chamfered",
  "type" : "top"
}
{
  "_id" : "CqhS2m2RcLZ2Bm4eb",
  "name" : "skirt_square",
  "type" : "skirt"
}
{
  "_id" : "dYP22ajALnWBwpBj2",
  "name" : "leg_square",
  "type" : "leg"
}

目录

{
  "_id" : "EcRGzPAq79giYKrbY",
  ...,
  "specs" : {
    ...,
    "models" : [
      {
        "mesh" : "Mwp5eYYZ4GZzvZuoK",
        "material" : "cf4KgXw7ZK6ukdzR7"
      },
      {
        "mesh" : "CqhS2m2RcLZ2Bm4eb",
        "material" : "cf4KgXw7ZK6ukdzR7"
      },
      {
        "mesh" : "dYP22ajALnWBwpBj2",
        "material" : "cf4KgXw7ZK6ukdzR7"
      }
    ]
  }
}

所需的聚合后返回的文档格式：

{
  "_id" : "EcRGzPAq79giYKrbY",
  ...,
  "specs" : {
    "dimensions" : {
      ...,
    },
    "models" : [
      {
        "mesh" : {
          "_id" : "Mwp5eYYZ4GZzvZuoK",
          "name" : "top_square_chamfered",
          "type" : "top"
        },
        "material" : {
          "_id" : "cf4KgXw7ZK6ukdzR7",
          "name" : "parquet_wood_mahogany"
        }
      },
      {
        "mesh" : {
          "_id" : "CqhS2m2RcLZ2Bm4eb",
          "name" : "skirt_square",
          "type" : "skirt"
        },
        "material" : {
          "_id" : "cf4KgXw7ZK6ukdzR7",
          "name" : "parquet_wood_mahogany"
        }
      },
      {
        "mesh" : {
          "_id" : "dYP22ajALnWBwpBj2",
          "name" : "leg_square",
          "type" : "leg"
        },
        "material" : {
          "_id" : "cf4KgXw7ZK6ukdzR7",
          "name" : "parquet_wood_mahogany"
        }
      }
    ]
  }
}

我没有包含任何查询代码，因为它离标记太远了，只不过是噪音。我一直在尝试使用

aggregate

，使用

$lookup

组合，但我没有达到我想要的效果。MongoDB v3.6

管道

语法将使这更容易。。。但我在v3.4中完全不知所措

我希望尽可能避免使用多个数据库请求来组合这些信息。如果您能提供任何建议，我们将不胜感激

编辑：工作解决方案-

db.catalog.aggregate([
  { "$lookup": {
    "from": 'models',
    "localField": "specs.models.mesh",
    "foreignField": "_id",
    "as": "models.mesh"
  }},
  { "$lookup": {
    "from": 'materials',
    "localField": "specs.models.material",
    "foreignField": "_id",
    "as": "models.material"
  }},
  { "$unwind": "$models.mesh" },
  { "$unwind": "$models.material" },
  { "$group":{
    "_id": "$_id",
    "title": { "$first": "$title" },
    "desc": { "$first": "$desc" },
    "thumbnail": { "$first": "$thumbnail" },
    "createdBy": { "$first": "$createdBy" },
    "createdAt": { "$first": "$createdAt" },
    "specs": { "$first": "$specs" },
    "models": { "$push": "$models" }
  }},
  { "$project": {
    "_id": "$_id",
    "title": "$title",
    "desc": "$desc",
    "thumbnail": "$thumbnail",
    "createdBy": "$createdBy",
    "createdAt": "$createdAt",
    "specs.dimensions": "$specs.dimensions",
    "specs.models": "$models",
  }}
])

---

你可以在下面试试

db.catalog.aggregate([
  { "$lookup": {
    "from": 'models',
    "localField": "specs.models.mesh",
    "foreignField": "_id",
    "as": "models.mesh"
  }},
  { "$lookup": {
    "from": 'materials',
    "localField": "specs.models.material",
    "foreignField": "_id",
    "as": "models.material"
  }},
  { "$unwind": "$models.mesh" },
  { "$unwind": "$models.material" },
  { "$group":{
    "_id": "$_id",
    "title": { "$first": "$title" },
    "desc": { "$first": "$desc" },
    "thumbnail": { "$first": "$thumbnail" },
    "createdBy": { "$first": "$createdBy" },
    "createdAt": { "$first": "$createdAt" },
    "specs": { "$first": "$specs" },
    "models": { "$push": "$models" }
  }},
  { "$project": {
    "title": "$title",
    "desc": "$desc",
    "thumbnail": "$thumbnail",
    "createdBy": "$createdBy",
    "createdAt": "$createdAt",
    "specs.dimensions": "$specs.dimensions",
    "specs.models": "$models",
  }}
])

---

谢谢你的回复。我正在尝试并调整您的查询，但没有返回任何结果

Models.collection.name

和

Materials.collection.name

更改为各自的名称<代码>模型和

材料

分别。可能您的

模型.集合.名称

/

材料.集合.名称

不正确。。。。否则它应该会起作用，我正在进行调整，它正在走到一起。你给我指明了正确的方向。models.mesh和models.materials需要规格。在他们面前。不需要第一个$REWIND。我马上会在这里再次发帖，差一点就明白了。@KyleRichardson明白了我做错了什么。。。请查看最新的答案，这就是我目前正在努力工作的内容。虽然它抛出了一个错误“specs字段必须是累加器对象”，但我发布了一个与我使用的查询相关的编辑。