How to find length of the array mongodb

Question

I have such this type of structure of my database. I want to find number of documents my \"JAN\" array contains. I am trying to do in different way but nothing works. That w

Answer 1

You can use $size operator to find the length of the array

db.collection.aggregate([
  {
    "$project": {
      "totalJan": {
        "$size": "$2017.JAN"
      }
    }
  }
])

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