mongodb: How to do group and aggregation on array fields

Question

Mongodb, a collection named 'blog' has a 'tags' field, just like this

blog1.tags=['javascript', 'node.js', 'express'] 
blog2.tags=['javascript', 'jquery']
blog3.tags=['javascript', 'node.js']

now I need a hot tag list, which like this

[['javascript', 3], ['node.js', 2], ['express', 1], ['jquery', 1]]

how can I do it?

Please do basic search by using a simple google search and you will find this: cookbook.mongodb.org/patterns/count_tags — user2665694
– user2665694, Commented Mar 20, 2011 at 7:49
You can use aggregation pipeline like group({"_id":"tags","count":{"$sum":1}}) — Ashish Bakwad
– Ashish Bakwad, Commented Dec 25, 2019 at 5:47

What Would Be Cool · Accepted Answer · 2012-04-23 16:54:41Z

2

In Mongodb 2.2 you will be able to use the aggregation framework and the $unwind and $group commands. Check out their demo here and the demo source code.

answered Apr 23, 2012 at 16:54

What Would Be Cool

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