在 mongodb 聚合中的阶段之后输出具有序列数字 id 的新集合

在MongoDB聚合管道中经过一些阶段后，我正在try 推出一个集合.

db.getCollection('MY_COLLECTION').aggregate([{
    $addFields: {
      "dataEntries.targetCol1": "$dataEntries.col1",
      "dataEntries.targetCol2": "$dataEntries.col2"
    }
  },
  {
    $project: {
      "_id": 0,
      "dataEntries.col1": 0,
      "dataEntries.col2": 0,
      "dataEntries.col3": 0,
      "dataEntries.col4": 0
    }
  },
  {
    $unionWith: {
      coll: "MY_COLLECTION",
      pipeline: [{
          $addFields: {
            "dataEntries.targetCol1": "$dataEntries.col3",
            "dataEntries.targetCol2": "$dataEntries.col4"
          }
        },
        {
          $project: {
            "_id": 0,
            "dataEntries.col1": 0,
            "dataEntries.col2": 0,
            "dataEntries.col3": 0,
            "dataEntries.col3": 0
          }
        }
      ]
    }
  },
  {
    $out: "test_out"
  }
])

结果集合包含一个objectId作为id.

/* 1 */
{
    "_id" : ObjectId("6239cb749482cf6b13248a80"),
    "dataEntries" : {
        "targetCol1" : "101-A",
        "targetCol2" : "101"
    }
}

/* 2 */
{
    "_id" : ObjectId("6239cb749482cf6b13248a81"),
    "dataEntries" : {
        "targetCol1" : "101-B",
        "targetCol2" : "101"
    }
}

有没有一种方法可以将每个文档的id设置为序列数字计数器？

/* 1 */
{
    "_id" : 1,
    "dataEntries" : {
        "targetCol1" : "101-A",
        "targetCol2" : "101"
    }
}

/* 2 */
{
    "_id" : 2,
    "dataEntries" : {
        "targetCol1" : "101-B",
        "targetCol2" : "101"
    }
}