Grouping documents in MongoDB and adding the document to an array

Question

The Problem: I currently have a list of documents that I would like to group by the attribute 'eventType'. The document (representing a song) currently look like this:

Song Document:
{
    id: ID,
    eventType: String,
    numberOfLikes: Integer,
    sections: String[]
}

Result: I would like to have these grouped by eventType, like as follows:

eventType: { 
    songs: [{
       songId: ID,
       numberOfLikes: Integer,
       sections: String[]
    }]
}

How would I do this using the MongoDB aggregation pipeline? I am using MongoDB 4.4.

turivishal · Accepted Answer · 2020-09-05 10:50:10Z

1

You can push root object in songs field using $$ROOT,

db.collection.aggregate([
  {
    $group: {
      _id: "$eventType",
      songs: { $push: "$$ROOT" }
    }
  }
])

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answered Sep 5, 2020 at 10:50

turivishal

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