MongoDB $lookup 聚合导致嵌套数组

Question

我有两个多对一关系的集合（多个主机的 http 服务通常提供“相同”服务，例如 DNS 级负载平衡）。 我正在尝试构建一个查询，返回合并为一个的相关文档（来自两个集合）。

主机集合：

{
    "_id" : ObjectId("60aa2485332483cb4f5e7122"),
    "ip" : "1.2.3.4",
    "services" : [
        {
            "proto" : "tcp",
            "port" : "22",
            "status" : "open",
            "reason" : "syn-ack",
            "ttl" : 53,
        },
        {
            "proto" : "tcp",
            "port" : "80",
            "status" : "open",
            "reason" : "syn-ack",
            "ttl" : 51,
            "http" : [
                ObjectId("60aa64c67d0bf23ce47c530c")
            ]
        }
    ],
    "version" : 4,
    "last_scanned" : 1621573240.730579,

https 合集：

{
    "_id" : ObjectId("60aa64c67d0bf23ce47c530c"),
    "vhost" : "test.com",
    "paths" : [
        {
            "path" : "/admin",
            "code" : 200
        },
        {
            "path" : "/stuff",
            "code" : 200
        }
    ]
}

我想编写一个查找，其中输出是这两个集合的组合。到目前为止，我能够将 https 文档放入主机中的顶级数组中：

db.hosts.aggregate([                                                                                                                                       
  {                                                                             
    $lookup:                                                                    
        {                                                                       
            from: "https",                                                      
            localField: "services.http",                                        
            foreignField: "_id",                                                
            as: 'http'                                                 
        }                                                                       
  }                                                                             
]).pretty()

最终结果为：

{
    "_id" : ObjectId("60aa2485332483cb4f5e7122"),
    "ip" : "1.2.3.4",
    "services" : [
        {
            "proto" : "tcp",
            "port" : "22",
            "status" : "open",
            "reason" : "syn-ack",
            "ttl" : 53,
        },
        {
            "proto" : "tcp",
            "port" : "80",
            "status" : "open",
            "reason" : "syn-ack",
            "ttl" : 51,
            "http" : [
                ObjectId("60aa64c67d0bf23ce47c530c")
            ]
        }
    ],
    "http" : [
        {
            "_id" : ObjectId("60aa64c67d0bf23ce47c530c"),
            "vhost" : "test.com",
            "paths" : [
                {
                    "path" : "/admin",
                    "code" : 200
                },
                {
                    "path" : "/stuff",
                    "code" : 200
                }
            ]
        }
    ]
    "version" : 4,
    "last_scanned" : 1621573240.730579
    ]
}

问题是我无法将“http”字段移动到通过查找 (services.$.http) 找到它的 ObjectId 的位置。我试图以各种方式修改 $lookup 的“as”字段，但没有成功。

甚至可以用“as”指向嵌套文档的较低级别吗？ 有什么解决方法可以实现这一点？

Answer 1

• $unwind解构服务数组
• $lookup 和 https 并将 as 设置为 services.http
• $group by _id 并重构 services 数组并设置其他必填字段

db.hosts.aggregate([
  { $unwind: "$services" },
  {
    $lookup: {
      from: "https",
      localField: "services.http",
      foreignField: "_id",
      as: "services.http"
    }
  },
  {
    $group: {
      _id: "$_id",
      ip: { $first: "$ip" },
      services: { $push: "$services" },
      version: { $first: "$version" },
      last_scanned: { $first: "$last_scanned" }
    }
  }
]).pretty()

Playground

---

没有$unwind的第二个选项，

• $lookup 与 https 合集
• $map 迭代 services 数组的循环
• $filter 迭代来自查找的 http 结果循环
• $ifNull 如果字段为空/未找到，将返回空 []
• $mergeObjects 合并services 的当前对象和过滤的http 数组
• http 现在不需要数组结果，所以使用 $$REMOVE 删除它

db.hosts.aggregate([
  {
    $lookup: {
      from: "https",
      localField: "services.http",
      foreignField: "_id",
      as: "http"
    }
  },
  {
    $addFields: {
      services: {
        $map: {
          input: "$services",
          as: "s",
          in: {
            $mergeObjects: [
              "$$s",
              {
                http: {
                  $filter: {
                    input: "$http",
                    cond: {
                      $in: ["$$this._id", { $ifNull: ["$$s.http", []] }]
                    }
                  }
                }
              }
            ]
          }
        }
      },
      http: "$$REMOVE"
    }
  }
])

Playground