How to find the data inside of array using mongoose

Question

I have a data like below in MongoDB.

const A = { uid: '1234',
            works: [
           { name: 'car',
             item:['tire','wheel']
           },
           { name: 'ship',
             item:['tire','wheel']
           }
           ]

My goal is to find whether the name duplicated exists or not.
In conclusion, I want to get only the names.
So 'res.send(result)' gives me like '[car, ship]'. But the code below doesn't work. How can I make that function? Thank you so much.

const workName = await User.findOne({
      uid: userID, works:{$in:['name']}
    });

Vim · Accepted Answer · 2019-08-16 05:58:24Z

1

The easy way is to find the aggregate of name and check if the count is greater than one. Since it is inside the the array we need to unwind it.

The below query works, to detect if a sub document contain duplicates for each document.

db.getCollection('collection_name').aggregate([{"$unwind":"$works"} ,{"$group":{"_id":{"name":"$works.name","uid":"$uid"},"count":{"$sum":1}}},{"$match":{"count":{"$gte":2}}}])

if you want to find in all the documents remove uid from _id of group.

answered Aug 16, 2019 at 5:58

Vim

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