arrays - MongoDB 图表 $multiply

Question

我有这样的数据。

"products": [{
        "_id": {
            "$oid": "5ffd0a8f6273740017cc5fca"
        },
        "name": "Banana",
        "price": 65,
        "createdAt": {
            "$date": "2021-01-12T02:33:51.648Z"
        },
        "updatedAt": {
            "$date": "2021-01-12T02:33:51.648Z"
        },
        "quantity": 3
    }, {
        "_id": {
            "$oid": "5ffd09326273740017cc5fb3"
        },
        "name": "Apple",
        "price": 79,
        "createdAt": {
            "$date": "2021-01-12T02:28:02.412Z"
        },
        "updatedAt": {
            "$date": "2021-01-12T02:28:02.412Z"
        },
        "quantity": 2
    }]

我想做的是将价格乘以数量。

执行：

{ $reduce: {
  input: '$products', initialValue: 0,
  in: { $multiply: ["$products.price",
      "$products.quantity"] } } 

我有一个错误$multiply 只支持数字类型，不支持数组