用reddit排序算法对mongodb进行排序

本文介绍了用reddit排序算法对mongodb进行排序的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

这是根据Reddit的排名算法对项目进行排名的js代码。

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

我的问题是：如何使用此代码对我的mongodb文档进行排名？

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; }

推荐答案

您可以使用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 ); };

运行mapReduce（不带减速器）：

And the run the mapReduce (without a reducer):

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

当然假设您的集合包含 ups ，缩减和日期。当然，排名需要以独特的方式发出，否则你需要一个减速器来分类结果。

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.

但一般来说应该做的。