如何在MongoDB中从每个子对象数组字段中为父对象添加值。

huangapple
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英文:

How to add value in parent from each child array of object field in mongodb

问题

我无法在数组的每个元素上添加字段。

我使用mongodb 3.6，假设我在mongodb中有以下文档：

  1. [
  2.   {
  3.     "_id": ObjectId("648fc2857edfa7ee4f1ce31c"),
  4.     "userId": "1",
  5.     "groups": [
  6.       {
  7.         "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  8.         "groupId": "1",
  9.         "groupLeads": [
  10.           {
  11.             "userId": "4"
  12.           },
  13.           {
  14.             "userId": "5"
  15.           }
  16.         ]
  17.       },
  18.       {
  19.         "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  20.         "groupId": "2",
  21.         "groupLeads": [
  22.           {
  23.             "userId": "2"
  24.           },
  25.           {
  26.             "userId": "3"
  27.           }
  28.         ]
  29.       }
  30.     ]
  31.   }
  32. ]

我想在groups数组下添加一个名为gLead的字段，所以我使用了聚合函数来执行如下操作：

  1. db.collection.aggregate([
  2.   {
  3.     "$addFields": {
  4.       "groups.gLead": {
  5.         "$map": {
  6.           "input": "$groups",
  7.           "as": "g",
  8.           "in": "$$g.groupLeads.userId"
  9.         }
  10.       }
  11.     }
  12.   }
  13. ])

为什么查询在第一个数组上返回如下结果：

  1. {
  2.   "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  3.   "gLead": [
  4.     [
  5.       "4",
  6.       "5"
  7.     ],
  8.     [
  9.       "2",
  10.       "3"
  11.     ]
  12.   ],
  13.   "groupId": "1",
  14.   "groupLeads": [
  15.     {
  16.       "userId": "4"
  17.     },
  18.     {
  19.       "userId": "5"
  20.     }
  21.   ]
  22. }

而不是如下所示：

  1. {
  2.   "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  3.   "gLead": [ "4", "5" ],
  4.   "groupId": "1",
  5.   "groupLeads": [
  6.     {
  7.       "userId": "4"
  8.     },
  9.     {
  10.       "userId": "5"
  11.     }
  12.   ]
  13. }

我应该使用哪个聚合查询？

MongoDB游乐场链接：https://mongoplayground.net/p/xokkBwgRR2s

英文:

I cannot add the fields on each element in an array

I use mongodb 3.6, let say that I have a this documents in mongodb

  1. [
  2.   {
  3.     "_id": ObjectId("648fc2857edfa7ee4f1ce31c"),
  4.     "userId": "1",
  5.     "groups": [
  6.       {
  7.         "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  8.         "groupId": "1",
  9.         "groupLeads": [
  10.           {
  11.             "userId": "4"
  12.           },
  13.           {
  14.             "userId": "5"
  15.           }
  16.         ]
  17.       },
  18.       {
  19.         "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  20.         "groupId": "2",
  21.         "groupLeads": [
  22.           {
  23.             "userId": "2"
  24.           },
  25.           {
  26.             "userId": "3"
  27.           }
  28.         ]
  29.       }
  30.     ]
  31.   },
  32. ]

I want to add a field under the groups array lets called gLead
so I use the aggregate function to do that like this

  1. db.collection.aggregate([
  2.   {
  3.     "$addFields": {
  4.       "groups.gLead": {
  5.         "$map": {
  6.           "input": "$groups",
  7.           "as": "g",
  8.           "in": "$$g.groupLeads.userId"
  9.         }
  10.       }
  11.     }
  12.   }
  13. ])

why the query return like this on first array

  1. {
  2.   "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  3.   "gLead": [
  4.     [
  5.       "4",
  6.       "5"
  7.     ],
  8.     [
  9.       "2",
  10.       "3"
  11.     ]
  12.   ],
  13.   "groupId": "1",
  14.   "groupLeads": [
  15.     {
  16.       "userId": "4"
  17.     },
  18.     {
  19.       "userId": "5"
  20.     }
  21.   ]
  22. },

instead of

  1. {
  2.   "_id": ObjectId("648fc2857edfa7ee4f1ce31d"),
  3.   "gLead": [ "4", "5" ],
  4.   "groupId": "1",
  5.   "groupLeads": [
  6.     {
  7.       "userId": "4"
  8.     },
  9.     {
  10.       "userId": "5"
  11.     }
  12.   ]
  13. },

what query of aggregate should I use?

mongodb playground: https://mongoplayground.net/p/xokkBwgRR2s

答案1

得分: 1

你是否正在寻找一个能够将$map处理后的信息与$mergeObject合并在一起的管道？类似于这样：

  1. db.collection.aggregate([
  2.   {
  3.     "$addFields": {
  4.       groups: {
  5.         "$map": {
  6.           "input": "$groups",
  7.           "as": "g",
  8.           "in": {
  9.             "$mergeObjects": [
  10.               "$$g",
  11.               {
  12.                 gLead: "$$g.groupLeads.userId"
  13.               }
  14.             ]
  15.           }
  16.         }
  17.       }
  18.     }
  19.   }
  20. ])

在这里演示

这个答案最初使用了$zip，但输出格式不太正确

英文:

Are you looking for a pipeline that $mergeObjects the $mapped information together? Something like this:

  1. db.collection.aggregate([
  2.   {
  3.     "$addFields": {
  4.       groups: {
  5.         "$map": {
  6.           "input": "$groups",
  7.           "as": "g",
  8.           "in": {
  9.             "$mergeObjects": [
  10.               "$$g",
  11.               {
  12.                 gLead: "$$g.groupLeads.userId"
  13.               }
  14.             ]
  15.           }
  16.         }
  17.       }
  18.     }
  19.   }
  20. ])

Playground demonstration here

This answer originally used $zip but the output format wasn't quite right

huangapple
  • 本文由 发表于 2023年6月19日 14:03:20
  • 转载请务必保留本文链接：https://go.coder-hub.com/76503977.html
  • aggregate
  • arrays
  • mongodb
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