包含数组查询中当前对象位置的Mongodb聚合addField

Question

在最后一个聚合管道之后，我接收到当前数组：

[{
    "cdrId": "61574b3e58fb1cae1494df2c",
    "date": "2021-10-01T17:54:06.057Z",
    "intentType": "FALLBACK"
},
{
    "cdrId": "61574b3e58fb1cae1494df2c",
    "date": "2021-10-01T17:54:06.057Z",
    "intentType": "FAQ"
},
{
    "cdrId": "61570b37522aba5e2f205356",
    "date": "2021-10-01T13:20:55.601Z",
    "intentType": "TRANS/DISAM"
},
{
    "cdrId": "61570b37522aba5e2f205356",
    "date": "2021-10-01T13:20:55.601Z",
    "intentType": "FAQ"
}]

我希望添加一个索引字段，显示对象在数组中的当前位置。输出将如下所示：

[{
    "index": 0,
    "cdrId": "61574b3e58fb1cae1494df2c",
    "date": "2021-10-01T17:54:06.057Z",
    "intentType": "FALLBACK"
},
{
    "index": 1,
    "cdrId": "61574b3e58fb1cae1494df2c",
    "date": "2021-10-01T17:54:06.057Z",
    "intentType": "FAQ"
},
{
    "index": 2,
    "cdrId": "61570b37522aba5e2f205356",
    "date": "2021-10-01T13:20:55.601Z",
    "intentType": "TRANS/DISAM"
},
{
    "index": 3,
    "cdrId": "61570b37522aba5e2f205356",
    "date": "2021-10-01T13:20:55.601Z",
    "intentType": "FAQ"
}]

如果下一个管道对这个数组进行排序，我将使用这个值。所以在分拣之前我有它原来的位置。

有什么办法能让我用聚合的方式做到这一点吗？我使用的是MongoDB 4.2。

Answer 1

试试这个：

db.collection.aggregate([
  // {$sort: {...} },
  {
    $group: {
      _id: null,
      data: { $push: "$$ROOT" }
    }
  },
  {
    $unwind: {
      path: "$data",
      includeArrayIndex: "index"
    }
  },
  {
    $replaceRoot: {
      newRoot: { $mergeObjects: [ "$data", {index: "$index"} ] }
    }
  }
])

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