如何在MongoDB中累积结果(使用forEach?)? [英] How to accumulate results (with forEach?) in MongoDB?

问题描述

假设我要搜索一个集合，扫描返回的结果集并对其进行一些转换.我尝试了以下代码:

Suppose I want to search through a collection, scan the returned result set and return some transformation of it. I've tried the following code:

db.my_collection.find({timestamp : {$gt: 1343032491799}}, {_id:0,sid:1}).limit(20).forEach(function(element) { print(element.sid); })

好的，效果很好.问题是:如何将结果(sid s)累积到一个数组中，而不是仅仅打印它们?

Ok, it worked well. To the question: how can I accumulate the results (sids) into an array instead of just printing them?

更新:当然首选(但不是必需)红宝石风格的单缸纸

Update: ruby-style one-liner is preferred (but not required) of course

推荐答案

在光标上调用toArray而不是forEach:

var a = db.my_collection.find(
    {timestamp : {$gt: 1343032491799}}, {_id:0,sid:1}).limit(20)
    .toArray().map(function(o){return o.sid;})

更新

似乎您可以跳过toArray并直接转到 ，因为光标直接提供了该方法:

Seems you can skip the toArray and go right to the map as the cursor provides that method directly:

var a = db.my_collection.find(
    {timestamp : {$gt: 1343032491799}}, {_id:0,sid:1}).limit(20)
    .map(function(o){return o.sid;})

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