mongoose/mongodb 查询多重排序 [英] mongoose/mongodb query multiple sort

问题描述

我对 mongodb 很陌生.我设法获得了仅基于 1 个参数的简单排序的基本概念.如果有超过 2 个排序参数怎么办.例如，在由具有属性 totalCuttingTime 和 favorited 的木工项目组成的数据库中.

i'm quite new to mongodb. i manage to get a basic idea of a simple sort based only 1 parameter. what if there are more than 2 sort parameters. for instance, in a database made up of woodworking projects that have attributes totalCuttingTime and favorited.

以下是否是正确的 mongoose/mongodb 函数，用于查找具有 least totalCuttingTime 的项目列表，并根据 highest favoriteCounts 排序到最低.

Is the following a correct mongoose/mongodb function to find a list of projects that have the least totalCuttingTime and order in according to highest favoriteCounts to lowest.

var ProjectModel= mongoose.model('Project', schema);

exports.getMinCuttingTime = function(number, callback){ 
    var leastCutTimeResult = ProjectModel.find().sort({totalCuttingTime: 1}).select({_id: 1}).limit(number).exec(
            function(err, projects) {
                callback(null, projects)
            }
        );

    var result = leastCutTimeResult.find().sort({favoriteCount: -1}).select({_id: 1}).limit(number).exec(
            function(err, projects) {
                callback(null, projects)
            }
        ); 

    return result;
}

推荐答案

您需要将两个 sort 项放在一个对象中:

You need to put both sort terms into one object:

exports.getMinCuttingTime = function(number, callback){ 
    ProjectModel.find()
        .sort({totalCuttingTime: 1, favoriteCount: -1})
        .select({_id: 1})
        .limit(number)
        .exec(
            function(err, projects) {
                callback(null, projects)
            }
        );
};

值得注意的是，Node.js 所基于的 ECMA-262 标准并没有规定维护对象的属性顺序，它只是匹配插入顺序的事实上的标准.为了消除任何疑问，您可以使用数组代替:

It's worth noting that the ECMA-262 standard on which Node.js is based doesn't specify that an object's property order is maintained, and it's only a de facto standard to match insertion order. To eliminate any doubt, you can use an array instead:

.sort([['totalCuttingTime', 1], ['favoriteCount', -1]])

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