具有投影的MongoDB查询没有嵌套字段且没有固定的父名称

如何解决具有投影的MongoDB查询没有嵌套字段且没有固定的父名称

我正在尝试通过使用投影的查询从MongoDB中检索一些文档。

文档看起来像这样：

{
    "_id": "01","country": "EUA","created": "2020-09-10T18:12:20.649Z","products": {
        "0001": {
            "id": "0001","price": "1.25","timestamp": "16004443546","class": "com.website.ecommerce.src.main.java.model.product"
        },"0123": {
            "id": "0123","price": "1.50","0443": {
            "id": "00443","price": "1.75","class": "com.website.ecommerce.src.main.java.model.product"
        }
    }
}

我不需要检索“ class”字段，因此在查询结果超过10k的情况下，该字段代表了响应大小的很大一部分。

collection.find({'_id': some_id},{'products.*._class': 0 })

我的猜测是有某种通配符可以胜任，但我找不到。

我尝试过：，$，$ ，$ **，** 但没有成功。

解决方法

//actual code output from mongoshell 4.2.6 on windows
//prepare the document in a collection called eua,as given in problem statement
> db.eua.find().pretty();
{
        "_id" : "01","country" : "EUA","created" : "2020-09-10T18:12:20.649Z","products" : {
                "0001" : {
                        "id" : "0001","price" : "1.25","timestamp" : "16004443546","class" : "com.website.ecommerce.src.main.java.model.product"
                },"0123" : {
                        "id" : "0123","price" : "1.50","0443" : {
                        "id" : "00443","price" : "1.75","class" : "com.website.ecommerce.src.main.java.model.product"
                }
        }
}
//use aggreate project command to first convert object to array in first stage
// use the project in 2nd stage to hide the class field
// reconvert back to original array to object with required fields marked as 1
> db.eua.aggregate([
...
... {
...     $project: {
...       _id: 1,...       country: 1,...       created: 1,...       prodToArray: {
...         $objectToArray: "$products"
...       }
...     }
...   },...   {
...     $project: {
...       "prodToArray.v.class": 0
...     }
...   },...   {
...       $project:{
...           _id: 1,...           country: 1,...           created: 1,...           products:{
...               $arrayToObject:"$prodToArray"
...           }
...       }
...   }
... ]).pretty()
{
        "_id" : "01","timestamp" : "16004443546"
                },"timestamp" : "16004443546"
                }
        }
}
>