問題描述

這是一個根據(jù) Reddit 的排名算法對項(xiàng)目進(jìn)行排名的 js 代碼.

Here is a js code to rank items according to Reddit's ranking algorithm.

我的問題是:如何使用此代碼對我的 mongodb 文檔進(jìn)行排名?

My question is: how do I use this code to rank my mongodb documents ?

(Reddit的排名算法)

function hot(ups,downs,date){
    var score = ups - downs;
    var order = log10(Math.max(Math.abs(score), 1));
    var sign = score>0 ? 1 : score<0 ? -1 : 0;
    var seconds = epochSeconds(date) - 1134028003;
    var product = order + sign * seconds / 45000;
    return Math.round(product*10000000)/10000000;
}
function log10(val){
  return Math.log(val) / Math.LN10;
}
function epochSeconds(d){
    return (d.getTime() - new Date(1970,1,1).getTime())/1000;
}

推薦答案

你可以使用mapReduce:

Well you can use mapReduce:

var mapper = function() {

    function hot(ups,downs,date){
        var score = ups - downs;
        var order = log10(Math.max(Math.abs(score), 1));
        var sign = score>0 ? 1 : score<0 ? -1 : 0;
        var seconds = epochSeconds(date) - 1134028003;
        var product = order + sign * seconds / 45000;
        return Math.round(product*10000000)/10000000;
    }

   function log10(val){
      return Math.log(val) / Math.LN10;
   }

   function epochSeconds(d){
       return (d.getTime() - new Date(1970,1,1).getTime())/1000;
   }

   emit( hot(this.ups, this.downs, this.date), this );

};

然后運(yùn)行 ??mapReduce(不使用 reducer):

And the run the mapReduce (without a reducer):

db.collection.mapReduce(
    mapper,
    function(){},
    {
        "out": { "inline": 1 }
    }
)

當(dāng)然，假設(shè)您的收藏"包含 ups、downs 和 date 字段.當(dāng)然，排名"需要以獨(dú)特"的方式發(fā)出，否則您需要一個reducer"來整理結(jié)果.

And of course presuming that your "collection" has the fields for ups, downs and date. Of course the "rankings" need to be emitted in a way that is "unique" otherwise you need a "reducer" to sort out the results.

但一般來說應(yīng)該可以完成這項(xiàng)工作.

But generally speaking that should do the job.

這篇關(guān)于通過reddit排名算法對mongodb進(jìn)行排序的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！