https://developers.weixin.qq.com/miniprogram/dev/wxcloud/reference-sdk-api/database/command/aggregate/AggregateCommand.in.html

我想实现如下效果

假设集合 shops 有如下记录：

{ "_id": 1, "topsellers": [{ id: 1, name: 'bread' }, { id:2, name: 'ice cream' }, { id: 3, name: 'butter' }] }
{ "_id": 2, "topsellers": [{ id: 2, name: 'ice cream' }, { id: 4, name: 'cheese' }, { id: 5, name: 'yagurt' }] }
{ "_id": 3, "topsellers": [{ id: 6, name: 'croissant' }, { id: 7, name: 'cucumber' }, { id: 8, name: 'coconut' }] }

标记销量最高的商品包含 ice cream 的记录。

const $ = db.command.aggregate
db.collection('price').aggregate()
  .project({
    included: $.in(['ice cream', '$topsellers'])
  })
  .end()

返回结果如下：

{ "_id": 1, "included": true }
{ "_id": 2, "included": true }
{ "_id": 3, "included": false }