MongoDB 检索具有最高值的数据

Question

我在 MongoDB 中有这个 collection:

[
  { _id: "...", "project": 244, "scanner": "powershell", "version": 2 },
  { _id: "...", "project": 244, "scanner": "powershell", "version": 3 },
  { _id: "...", "project": 244, "scanner": "powershell", "version": 4 },
  { _id: "...", "project": 244, "scanner": "powershell", "version": 4 }
]

我需要检索所有具有最高版本的文档，在这种情况下：

  { _id: "...", "project": 244, "scanner": "powershell", "version": 4 },
  { _id: "...", "project": 244, "scanner": "powershell", "version": 4 }

能找到最高的版本，按-1排序取第一个

如何将找到的结果应用于过滤器？

非常感谢

Answer 1

playground

db.collection.aggregate([
  {
    "$group": { //Find max value
      "_id": "null",
      "maxV": {
        "$max": "$version"
      },
      data: { // add all records to this array
        $push: "$$ROOT"
      }
    }
  },
  {
    $project: {
      "output": {
        $filter: {//Filter the matching record from the array in stage 1
          input: "$data",
          as: "d",
          cond: {
            $eq: [
              "$$d.version",
              "$maxV"
            ]
          }
        }
      },
      "_id": 0
    }
  }
])

如果你想摆脱关键 output，你可以像 this play

那样多两个阶段

  {
    "$unwind": "$output"
  },
  {
    "$replaceRoot": {
      "newRoot": "$output"
    }
  }

MongoDB 检索具有最高值的数据

MongoDB retrieve data with highest value

sorting

aggregate

max

match

mongodb