node.js - 我在使用 `$unwind` 时获取了数组的分隔文档。如何将它们作为数组获取？

Question

这是我的架构

{
    "productid": {type: mongoose.Schema.Types.ObjectId, ref: 'products', required: true},
    "itemcode": {type: String, required: true},
    "itemname": {type: String, required: true/*, index: "text"*/},
    "itemdescription": {type: String, required: true},
    "itemimgurl": {type: String, required: true},
    "mainprice": {type: Number},
    "offerprice": {type: Number, required: true},
    "unit": {type: String, required: true},
    "offertag": {type: String},
    "itemprice":[
        {
            "itemname" :{type: String, required: true},
            "unit": {type: String, required: true},
            "offerprice": {type: Number, required: true},
            "mainprice": {type: Number},
            "stock": {type: Number, required: true},
            "notify": {type: Number, required: true},
            "status": {type: Boolean, required: true},
            "itemimgurl": {type: String},
            "offertag": {type: String}
        }
    ]
}

现在我需要查询整个文档，其中stock的文档小于notify。我怎样才能实现这个目标？

我尝试过这样

subproduct.aggregate(
       [
         {$unwind: "$itemprice"},
         {$project:
           {"productid": 1,
            "itemcode": 1,
            "itemname": 1,
            "itemdescription": 1,
            "itemimgurl": 1,
            "mainprice": 1,
            "offerprice": 1,
            "unit": 1,
            "offertag": 1,
            "itemprice":1,
            "diff": {$subtract: ["$itemprice.stock", "$itemprice.notify"]}}},
         {"$match": {'diff': {'$lt': 0}}}]

我正在单独收到响应，但我需要响应，因为它就像模式一样，我的意思是，即使数组中的一个文档与查询匹配，它也应该按原样返回主文档，而不会拆分为不同的文档。有可能变成这样吗？

Answer 1

要逆转 $unwind 的效果，我们可以使用聚合运算符 $push。

因此请尝试以下查询，

 subproduct.aggregate(
             {$unwind: "$itemprice"},  
{$project:
               {
            "productid": 1,
                "itemcode": 1,
                "itemname": 1,
                "itemdescription": 1,
                "itemimgurl": 1,
                "mainprice": 1,
                "offerprice": 1,
                "unit": 1,
                "offertag": 1,
                "itemprice":1,
                "diff": {$subtract: ["$itemprice.stock", "$itemprice.notify"]}}},
             {"$match": {'diff': {'$lt': 0}}},

             {$group:{_id:"$_id",
                "productid":{"$first":"$productid"},
                 "itemcode": {"$first":"$itemcode"},
                "itemname": {"$first":"$itemname"},
                "itemdescription": {"$first":"$itemdescription"},
                "itemimgurl": {"$first":"$itemimgurl"},
                "mainprice": {"$first":"$mainprice"},
                "offerprice": {"$first":"$offerprice"},
                "unit": {"$first":"$unit"},
                "offertag": {"$first":"$offertag"},
                "itemprice":{$push:"$itemprice"}}}]);