如何仅投影MongoDB阵列中的字段？

发布于 2025-01-23 04:30:55 字数 650 浏览 1 评论 0原文

有一个文档架构，该模式具有一个名为“ updatedFields”的数组字段，其中包含一些您会在“ OldDocument”和 “ newDocument”对象。这是它的图片。

现在我只想投射“ updatedFields”中存在的那些字段来自“ newDocument” and 和“ olddocument” 如下：

 $project : { 
    "oldDocument.Modified":1,
    "oldDocument.Status":1,
    "newDocument.Modified":1,
    "newDocument.Status":1
 }

有人知道如何在数组中的字段名称上构建项目子句基础吗？我需要mongoDB查询，而不是JS代码。

原文

there is a document schema that has an array field called "updatedFields" which contains some fields names that you will find in "oldDocument" and
"newDocument" objects. Here is its picture.

Now I want to project only those fields which exist in "updatedFields" array from "newDocument" and "oldDocument" like below:

 $project : { 
    "oldDocument.Modified":1,
    "oldDocument.Status":1,
    "newDocument.Modified":1,
    "newDocument.Status":1
 }

Does anyone know how to build the project clause base on the fields' names in the array? I need a MongoDB query, not js code.

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

飞烟轻若梦 2025-01-30 04:30:55

您可以使用$ objectToArray为了将键格式化为值，$ filter根据UPDATEDFIELDS array，然后使用$ $ ArrayToObject将它们再次制成键。

编辑：根据评论的请求，使用$ MAP在过滤器内部使用将日期投入到字符串。

像这样的事情：

db.collection.aggregate([
  {
    $project: {
      oldDocumentArr: {$objectToArray: "$oldDocument"},
      newDocumentArr: {$objectToArray: "$newDocument"},
      updatedFields: 1
    }
  },
  {
    $project: {
      oldDocumentFilter: {
        $map: {
          input: {
            $filter: {
              input: "$oldDocumentArr",
              as: "item",
              cond: {$in: ["$item.k", "$updatedFields"]
              }
            }
          },
          "as": "obj",
          "in": {
            "k": "$obj.k",
            "v": {$toString: "$obj.v"}
          }
        }
      },
      newDocumentFilter: {
        $map: {
          input: {
            $filter: {
              input: "$newDocumentArr",
              as: "item",
              cond: {$in: ["$item.k", "$updatedFields"]
              }
            }
          },
          "as": "obj",
          "in": {
            "k": "$obj.k",
            "v": {$toString: "$obj.v"}
          }
        }
      }
    }
  },
  {
    $project: {
      oldDocument: {$arrayToObject: "$oldDocumentFilter"},
      newDocument: {$arrayToObject: "$newDocumentFilter"},
      _id: 0
    }
  }
])

如您在 Playground ）

You can use $objectToArray in order to format the keys as values, $filter them according to the updatedFields array and then use $arrayToObject to make them keys again.

Edit: using $map inside the filter to cast dates to strings, according to a request on the comments.

Something like this:

db.collection.aggregate([
  {
    $project: {
      oldDocumentArr: {$objectToArray: "$oldDocument"},
      newDocumentArr: {$objectToArray: "$newDocument"},
      updatedFields: 1
    }
  },
  {
    $project: {
      oldDocumentFilter: {
        $map: {
          input: {
            $filter: {
              input: "$oldDocumentArr",
              as: "item",
              cond: {$in: ["$item.k", "$updatedFields"]
              }
            }
          },
          "as": "obj",
          "in": {
            "k": "$obj.k",
            "v": {$toString: "$obj.v"}
          }
        }
      },
      newDocumentFilter: {
        $map: {
          input: {
            $filter: {
              input: "$newDocumentArr",
              as: "item",
              cond: {$in: ["$item.k", "$updatedFields"]
              }
            }
          },
          "as": "obj",
          "in": {
            "k": "$obj.k",
            "v": {$toString: "$obj.v"}
          }
        }
      }
    }
  },
  {
    $project: {
      oldDocument: {$arrayToObject: "$oldDocumentFilter"},
      newDocument: {$arrayToObject: "$newDocumentFilter"},
      _id: 0
    }
  }
])

As you can see on the playground

回复收藏 0 原文

~没有更多了~