javascript - 使用属性数组查询 Mongoose HashMap ？

Question

我有一个名为 csgoItems 的 Mongoose 文档和架构，如下所示:

{
    "_id": {
        "$oid": "56ff8fb815ad7ecdede3bc3c"
    },
    "csgo_number": 1,
    "last_updated": 1459589048324,
    "items": {
        "Shadow Daggers | Urban Masked (Well-Worn)": {
            "market_hash_name": "Shadow Daggers | Urban Masked (Well-Worn)",
            "sale_price": 134.29
        },
        "Shadow Daggers | Urban Masked (Minimal Wear)": {
            "market_hash_name": "Shadow Daggers | Urban Masked (Minimal Wear)",
            "sale_price": 108.3
        },
        "Shadow Daggers | Urban Masked (Field-Tested)": {
            "market_hash_name": "Shadow Daggers | Urban Masked (Field-Tested)",
            "sale_price": 79.73
        },
        "Shadow Daggers | Urban Masked (Battle-Scarred)": {
            "market_hash_name": "Shadow Daggers | Urban Masked (Battle-Scarred)",
            "sale_price": 73.17
        },
        "Shadow Daggers | Stained (Well-Worn)": {
            "market_hash_name": "Shadow Daggers | Stained (Well-Worn)",
            "sale_price": 113.25
        }
    }
}

我正在尝试使用 market_hash_names 数组来返回仅包含那些市场哈希名称的项目列表，如下所示

var searchItems = ["Shadow Daggers | Stained (Well-Worn)", "Shadow Daggers | Urban Masked (Battle-Scarred)"]

我已经尝试过了

    csgoItems.find({"items": {$in: searchItems}}, function(err, found){
        if(err){
            console.log(err);
        }else{
            console.log(found);
        }

我怎样才能达到这些结果？

Answer 1

查询不起作用，因为 $in运算符仅适用于数组。

要根据哈希属性过滤查询结果，您需要使用 MongoDB 的 mapReduce

一个简单的解决方案是:

1. 定义一个函数将 HashMap 转换为数组

   function hashToArray(hash) {
     return Object.keys(hash).map(function(key) {
       return hash[key];
     });
   }
   

2. 定义mapReduce查询的选项

   hashToArray 函数将用于将每个文档的 items 哈希值转换为数组。

   var options = {};
   options.map = function (){ 
     emit(this._id, hashToArray(this.items), 1);
   }
   options.reduce = function (key, values){ 
     return values[0];
   }
   

3. 执行 map 缩减并针对结果运行查询

   csgoItems.mapReduce(options, function(err, model, stats) {
     model.find({"items.market_hash_name": {$in: searchItems}},   function(err, foundItems){
       // use the result
     });
   });