MongoDB。如何在数组中将字段从一个子文档移动到另一个子文档？

{
  "_id": 1,
  "subdocuments": [
    {
      "field1": "value1",
      "field2": "value2"
    },
    {
      "field3": "value3",
      "field4": "value4"
    }
  ]
}

db.collection.update(
  { "_id": 1 }, // 匹配条件
  { $push: { "subdocuments.0": { "field3": "$subdocuments.1.field3" } } } // 更新操作
)

{
  "_id": 1,
  "subdocuments": [
    {
      "field1": "value1",
      "field2": "value2",
      "field3": "value3"
    },
    {
      "field4": "value4"
    }
  ]
}