流星:如何仅搜索与Mongo类似的collection.distinct("fieldname")的不同字段值 [英] Meteor: how to search for only distinct field values aka a collection.distinct("fieldname") similar to Mongo's

问题描述

我正在使用Meteor，并且试图查找字段的唯一(唯一)值. Mongodb具有命令

I'm using Meteor, and I'm trying to find only distinct (unique) values of a field. Mongodb has the command

Collection.distinct("fieldname");

，但是在Mongo的Meteor驱动程序中未实现. 我已经尝试过使用meteor-mongo-extensions包，但是在客户端控制台上对于客户端Collection.distinct("fieldname");

but it's not implemented in the Meteor driver for Mongo. I've tried using the meteor-mongo-extensions package but still got an "undefined" on the client console for a client-side Collection.distinct("fieldname");

本质上是什么在寻找?

what, essentially, is a distinct looking for?

我觉得有人这是一个基本的查询-例如，以学生为老师的学生列表，然后由老师列出学生的列表，例如...

I feel like someone this is such a basic query- like for example a list of students with their teacher as a field, and then making a list of students by teachers out of that, for example...

如果我可以将懒惰的大脑包裹在一般概念上，那么我可能可以解决一些可行的问题.

if I can just wrap my lazy errant brain around the general concept I can probably bash something workable out.

推荐答案

您可以只使用Meteor随附的underscore.js-对于建议的用例应该没问题.如果您在庞大的数据集上尝试或重复运行它，可能会遇到性能问题，但是对于普通或园艺用途而言，它应该足够了:

You can just use underscore.js, which comes with Meteor - should be fine for the suggested use case. You might run into performance problems if you try this on a vast data set or run it repeatedly, but it should be adequate for common-or-garden usage:

var distinctEntries = _.uniq(Collection.find({}, {
    sort: {myField: 1}, fields: {myField: true}
}).fetch().map(function(x) {
    return x.myField;
}), true);

这将为Collection中的所有文档返回myField中的不同条目.如果单线看上去有点笨拙，则表示歉意； sort和fields选项以及true标志只是为了提高效率.

That will return the distinct entries in myField for all documents in Collection. Apologies if the one-liner looks a bit unwieldy; the sort and fields options and the true flag are just to make it more efficient.

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