MongoDB聚合用于基于ID过滤列表并将此过滤列表映射到另一个字段

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英文:

MongoDb aggregation for filtering list based on ids and mapping this filtered list to another field

问题

以下是您提供的内容的翻译结果：

在我的 MongoDB 中，数据如下所示：

  1. {
  2.   "classes": [
  3.     {
  4.       "classId": "SSC",
  5.       "studentIds": [
  6.         "1"
  7.       ]
  8.     },
  9.     {
  10.       "classId": "HSC",
  11.       "studentIds": [
  12.         "2",
  13.         "3"
  14.       ]
  15.     }
  16.   ],
  17.   "students": [
  18.     {
  19.       "_id": "1",
  20.       "student": {}
  21.     },
  22.     {
  23.       "_id": "2",
  24.       "student": {}
  25.     },
  26.     {
  27.       "_id": "3",
  28.       "student": {}
  29.     }
  30.   ] 
  31. }

我希望进行聚合查询，使其返回如下所示的数据：

  1. "classes": [
  2.     {
  3.       "classId": "SSC",
  4.       "students": [
  5.         {
  6.           "id": "1",
  7.           "student": {}
  8.         }
  9.       ]
  10.     },
  11.     {
  12.       "classId": "HSC",
  13.       "students": [
  14.         {
  15.           "id": "2",
  16.           "student": {},
  17.         },
  18.         {
  19.           "id": "3",
  20.           "student": {},
  21.         }
  22.       ]
  23.     }
  24.   ]

在这个问题中，我有一系列的 ID。它应该过滤该 ID 的学生列表，然后获取该对象，并将该对象放入班级数组中。

我尝试使用 MongoDB 聚合来解决这个问题。但不幸的是，我无法为此编写查询。那么，我们能否使用聚合来实现上述情况呢？

我正在使用 Spring Boot 的 mongoTemplate。

英文:

In my mongodb I have the data as shown below:

  1. {
  2.   "classes": [
  3.     {
  4.       "classId": "SSC",
  5.       "studentIds": [
  6.         "1"
  7.       ]
  8.     },
  9.     {
  10.       "classId": "HSC",
  11.       "studentIds": [
  12.         "2",
  13.         "3"
  14.       ]
  15.     }
  16.   ],
  17.   "students": [
  18.     {
  19.       "_id": "1",
  20.       "student": {}
  21.     },
  22.     {
  23.       "_id": "2",
  24.       "student": {}
  25.     },
  26.     {
  27.       "_id": "3",
  28.       "student": {}
  29.     }
  30.   ], 
  31. }

And I want an aggregation query such that it returns the data as shown below:

  1. "classes": [
  2.     {
  3.       "classId":"SSC",
  4.       "students": [
  5.         {
  6.           "id": "1",
  7.           "student": {}
  8. 	    }
  9.       ]
  10.     },
  11.     {
  12.       "classId":"HSC",
  13.       "students": [
  14.         {
  15.           "id": "2",
  16.           "student": {},
  17.  	    },
  18.         {
  19.           "id": "3",
  20.           "student": {}
  21.  	    }
  22.       ]
  23.     }
  24.   ]

In this I have list of ids. It should filter the students list for that id and take that object and place this object in class array.

I have tried to use mongodb aggregation for this problem. But unfortunately I am not able write query for that. So can we achieve the above scenario using aggregation.

I am using spring boot mongoTemplate.

答案1

得分: 1

你可以使用$map和$filter，

  • 使用$map操作在classes数组中创建students字段，并在students数组中进行$filter操作，检查数组中是否存在符合条件的ids。
  1. db.collection.aggregate([
  2.   {
  3.     $project: {
  4.       classes: {
  5.         $map: {
  6.           input: "$classes",
  7.           as: "c",
  8.           in: {
  9.             classId: "$$c.classId",
  10.             students: {
  11.               $filter: {
  12.                 input: "$students",
  13.                 cond: { $in: ["$$this._id", "$$c.studentIds"] }
  14.               }
  15.             }
  16.           }
  17.         }
  18.       }
  19.     }
  20.   }
  21. ])

Playground

英文:

You can use $map and $filter,

  • $map input classes array create students field and do $filter in students array and check condition ids in array or not
  1. db.collection.aggregate([
  2.   {
  3.     $project: {
  4.       classes: {
  5.         $map: {
  6.           input: "$classes",
  7.           as: "c",
  8.           in: {
  9.             classId: "$$c.classId",
  10.             students: {
  11.               $filter: {
  12.                 input: "$students",
  13.                 cond: { $in: ["$$this._id", "$$c.studentIds"] }
  14.               }
  15.             }
  16.           }
  17.         }
  18.       }
  19.     }
  20.   }
  21. ])

Playground

huangapple
  • 本文由 发表于 2020年9月9日 03:32:30
  • 转载请务必保留本文链接：https://go.coder-hub.com/63800466.html
  • aggregation
  • java
  • mongodb
  • mongodb-query
  • spring-boot
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