如何在猫鼬中使用聚合

本文介绍了如何在猫鼬中使用聚合的处理方法，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

如何在猫鼬中定义以下MongoDB聚合查询:

How do I define the following MongoDB aggregate query in mongoose:

db.contacts.aggregate([{$group: { "_id": { code: "$Code", name: "$Name" } } }])

查询的目的是提取一系列不同的代码和名称.

The objective of the query is to pull a list of distinct codes and names.

我当前的模型代码是:

'use strict'; var mongoose = require('mongoose'), Schema = mongoose.Schema, ObjectId = Schema.ObjectId; var fields = { Code: { type: String }, Name: { type: String } }; var contactSchema = new Schema(fields); module.exports = mongoose.model('Contacts', contactSchema);

路由器看起来像这样:

api.contacts = function (req, res) { Contacts.find({ AgencyTranslation: /^BROADCASTING/ }, function(err, contacts) { if (err) { res.json(500, err); } else { res.json({contacts: contacts}); } });

我尝试了各种变体，还查看了以下示例代码: mongoose API文档 ，但似乎无法正常工作.

I tried various variations, also looked up the sample code at: mongoose API docs, but I cannot seem to get it working.

(注意:以上查询在MongoDB控制台中确实有效.)

(Note: the above query does work in the MongoDB console.)

推荐答案

尝试一下

Contacts.aggregate({$group: { "_id": { code: "$Code", name: "$Name" } } }, function(err, contacts) { ... });

或者，如果需要此AgencyTranslation: /^BROADCASTING/条件，请使用$match

Or, with $match if you need this AgencyTranslation: /^BROADCASTING/ condition

Contacts.aggregate([ { $match : { AgencyTranslation: /^BROADCASTING/ } }, { $group: { "_id": { code: "$Code", name: "$Name" } } } ], function(err, contacts) { // ... });