Mongo 根据数组中子文档的值进行迁移以设置值

Question

我有这样的文档结构：

_id: "xx"
statuses: [{
  status: "pending",
  timestamp: "1 january 10 pm",
}, {
  status: "accepted",
  timestamp: "2 january 2 am",
}]

现在我想在根结构中添加接受的时间戳。

_id: "xx"
statuses: [{
  status: "pending",
  timestamp: "1 january 10 pm",
}, {
  status: "accepted",
  timestamp: "2 january 2 am",
}]
last_accepted_at: "2 january 2 am"

我知道如何根据另一个根字段设置值，但不知道如何根据我必须过滤的数组项设置值。

我试过了：

db.task.findOneAndUpdate( { last_accepted_at: { $exists: false } }, { $set: { "last_accepted_at": "statuses.$[element].timestamp" }}, { arrayFilters: [ { "element.status": "accepted" } ] },  )

有错误

uncaught exception: Error: findAndModifyFailed failed: {
    "ok" : 0,
    "errmsg" : "The array filter for identifier 'element' was not used in the update { $set: { last_accepted_at: \"statuses.$[element].timestamp\" } }",
    "code" : 9,
    "codeName" : "FailedToParse"
} :

我也试过：

db.task.findOneAndUpdate( { last_accepted_at: { $exists: false } }, { $set: { "last_accepted_at": "statuses.$[element].timestamp" }}, { arrayFilters: [ { "element.$.status": "accepted" } ] },  )
uncaught exception: Error: findAndModifyFailed failed: {
    "ok" : 0,
    "errmsg" : "The array filter for identifier 'element' was not used in the update { $set: { last_accepted_at: \"statuses.$[element].timestamp\" } }",
    "code" : 9,
    "codeName" : "FailedToParse"
} :

如何实现？我也想使用 updateMany 因为它是一个迁移文件来更新所有旧数据。谢谢

Answer 1

"The array filter for identifier 'element' was not used in the update { $set: { last_accepted_at: "statuses.$[element].timestamp" } }",

错误提示您不能将 arrayFilters 用作任何字段的值，您只能将其用作键的一部分，有关详细信息，请参阅 $[<identifier>]、

其次，普通更新查询不允许内部字段作为另一个字段的值，需要使用update with aggregation pipeline从MongoDB 4.2开始，

$filter 迭代 statuses 数组的循环并获得“已接受”状态结果
$arrayElemAt 从上面过滤的结果中获取第一个元素
$set 从上面的 arrayElemAt 操作

timestamp

db.task.updateMany({
  last_accepted_at: { $exists: false },
  "statuses.status": "accepted"
},
[
  {
    $set: {
      last_accepted_at: {
        $arrayElemAt: [
          {
            $filter: {
              input: "$statuses",
              cond: { $eq: ["$$this.status", "accepted"] }
            }
          },
          0
        ]
      }
    }
  },
  {
    $set: { last_accepted_at: "$last_accepted_at.timestamp" }
  }
])

Playground

Mongo 根据数组中子文档的值进行迁移以设置值

Mongo make migration to set value based on value of a subdocument in array

document

database-migration

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