带有查找的外部集合的MongoDB条件

Question

我在 MongoDB 4.0 (pymongo) 中有三个集合

users: [
{_id: "aaa", name: "John", user_type: "writer", department: {value: "1", label:"press"}},
{_id: "bbb", name: "Charles", user_type: "writer", department: {value: "1", label:"press"}},
{_id: "ccc", name: "Jessy", user_type: "admin_writer", department: {value: "1", label:"press"}},
{_id: "ddd", name: "Tim", user_type: "writer", department: {value: "2", label:"news"}},
{_id: "eee", name: "Max", user_type: "admin_writer", department: {value: "2", label:"news"}},
{_id: "fff", name: "Julia", user_type: "admin", department: {value: "2", label:"news"}},
{_id: "ggg", name: "Arnold", user_type: "writer", department: {value: "3", label:"infos"}}
]

departments: [
{_id: 1, name: "press", group: "times"},
{_id: 2, name: "news", group: "times"},
{_id: 3, name: "infos", group: "herald"}
]

docs: [
{_id: 1, name: "monday", user_id: "aaa"},
{_id: 2, name: "tuesday", user_id: "bbb"},
{_id: 3, name: "wednesday", user_id: "ddd"},
{_id: 4, name: "thursday", user_id: "ddd"},
{_id: 5, name: "friday", user_id: "ggg"}
]

在我的示例中，用户可以编写文档并在部门工作。部门由组（社会）定义。作家只能看到他的文档，admin_writer 可以看到他部门的所有文档，包括他编写的文档，管理员可以看到组中的所有文档，即使他在特定部门工作。

当用户登录应用程序时，我需要在仪表板中列出所有文档

例如，结果将是：

John (writer) : [{name: "monday"}]
Jessy (admin_writer) : [{name: "monday"}, {name: "tuesday"}]
Max (admin_writer) : [{name: "wednesday"}, {name: "thursday"}]
Julia (admin) : [{name: "monday"}, {name: "tuesday"},{name: "wednesday"}, {name: "thursday"}]
Arnold (writer) : [{name: "friday"}]

为此，我管理每个特定 user_type 的查询。对于作家，我使用 $match 因为 user_id 直接在 docs 集合中，但对于其他两个 user_type，我需要使用 $lookup 在外部集合中添加条件。我尝试了两种方法（我使用 Pymongo）：

user_department = 1

db.docs.aggregate([{
            '$lookup': {
                'from': "users",
                'localField': "user_id",
                'foreignField': "_id",
                'as': "user"
            }
        },{
                "$addFields": {
                    "user": {
                        "$arrayElemAt": [
                            {
                                "$filter": {
                                    "input": "$user",
                                    "as": "userId",
                                    "cond": {
                                        "$eq": ["$$userId.department.value", user_department]
                                    }
                                }
                            }, 0
                        ]
                    }
                }
            }, {'$project: {'name': 1}]);

或

db.docs.aggregate([{
                "$lookup": {
                    "from": "users",
                    "let": {
                        'id': "$user_id"
                    },
                    "pipeline": [
                        {
                            '$match': {
                                '$expr': {
                                    '$eq': [
                                        "$_id",
                                        "$$id"
                                    ]},
                                "_id": user_department
                            }
                        }
                    ],
                    "as": "user"
                }
            }]);

在我的两次尝试中，我没有预期的结果。当我与 admin_writer (Jessy) 联系时，我也有来自其他部门和小组的“星期五”文档。如果您知道它发生的原因或其他解决方案，谢谢

Answer 1

您可以将查找的文档分为 3 种情况：

1. 用户可以自己查看的文档
2. 如果他/她是 admin_writer 用户可以按部门查看的文档
3. 如果他/她是管理员，用户可以查看的文档（即所有文档） 可查看文档的最终列表将是上述 3 种情况的结合。

用户可以自己查看的文档

一个简单的$lookup 就足够了

{
    "$lookup": {
      "from": "docs",
      "localField": "_id",
      "foreignField": "user_id",
      "as": "selfDocs"
    }
}

如果他/她是 admin_writer 用户可以按部门查看的文档

您首先需要获取同一部门的完整用户列表。添加$and 条件和子管道中的查找以检查所有部门用户的 user_type 和文档

{
    "$lookup": {
      "from": "users",
      "localField": "department.value",
      "foreignField": "department.value",
      "as": "deptUsers"
    }
},
{
    "$lookup": {
      "from": "docs",
      "let": {
        userType: "$user_type",
        deptUsers: "$deptUsers"
      },
      pipeline: [
        {
          $match: {
            $expr: {
              $and: [
                {
                  $eq: [
                    "$$userType",
                    "admin_writer"
                  ]
                },
                {
                  $in: [
                    "$user_id",
                    "$$deptUsers._id"
                  ]
                }
              ]
            }
          }
        }
      ],
      "as": "deptDocs"
    }
}

如果用户是管理员则可以查看的文档（即所有文档）

$lookup部门查找用户所在的组。然后使用用户的组来查找组内的所有用户。对user_type: "admin" 进行条件检查，该文档属于同一组中的用户。

{
    "$lookup": {
      "from": "departments",
      let: {
        dept: "$department.value"
      },
      pipeline: [
        {
          $match: {
            $expr: {
              $eq: [
                "$$dept",
                {
                  $toString: "$_id"
                }
              ]
            }
          }
        }
      ],
      "as": "group"
    }
  },
  {
    "$unwind": "$group"
  },
  {
    "$set": {
      "group": "$group.group"
    }
  },
  {
    "$lookup": {
      "from": "users",
      "let": {
        group: "$group"
      },
      "pipeline": [
        {
          "$lookup": {
            "from": "departments",
            let: {
              d: "$department.value"
            },
            pipeline: [
              {
                $match: {
                  $expr: {
                    $eq: [
                      "$$d",
                      {
                        $toString: "$_id"
                      }
                    ]
                  }
                }
              }
            ],
            "as": "gp"
          }
        },
        {
          "$unwind": "$gp"
        },
        {
          $match: {
            $expr: {
              $eq: [
                "$gp.group",
                "$$group"
              ]
            }
          }
        },
        {
          "$project": {
            "_id": 1
          }
        }
      ],
      "as": "groupUsers"
    }
  },
  {
    "$lookup": {
      "from": "docs",
      "let": {
        userType: "$user_type",
        groupUsers: "$groupUsers"
      },
      pipeline: [
        {
          $match: {
            $expr: {
              $and: [
                {
                  $eq: [
                    "$$userType",
                    "admin"
                  ]
                },
                {
                  $in: [
                    "$user_id",
                    "$$groupUsers._id"
                  ]
                }
              ]
            }
          }
        }
      ],
      "as": "adminDocs"
    }
  }

使用$setUnion 将它们链接起来

allDocs: {
  "$setUnion": [
    "$selfDocs",
    "$deptDocs",
    "$adminDocs"
  ]
}

这是Mongo playground 供您参考。