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 would be great if someone helps.

 {
            "_id" : ObjectId("5cd8609db20663a19e2c362c"),
            "2017" : {
                "JAN" : [
                    {
                        "SYMBOL" : "20MICRONS",
                        "SERIES" : "EQ",
                        "OPEN" : "33.4",
                        "HIGH" : "34.3",
                        "LOW" : "33",
                    },
                    {
                        "SYMBOL" : "3IINFOTECH",
                        "SERIES" : "EQ",
                        "OPEN" : "5.8",
                        "HIGH" : "5.8",
                        "LOW" : "5.55",
                    },
                    {
                        "SYMBOL" : "3MINDIA",
                        "SERIES" : "EQ",
                        "OPEN" : "11199.9",
                        "HIGH" : "11233",
                        "LOW" : "10861",
                    }
                ]
            }
        }

Possible duplicate of [MongoDB: count the number of items in an array](https://stackoverflow.com/questions/21387969/mongodb-count-the-number-of-items-in-an-array) — str, May 12 '19 at 18:23
I did what is mentioned in that post but can't achieve results, that's why I posted new question. — Yash Choksi, May 12 '19 at 18:24
@yashChoksi You will have to be more specific than "can't achieve results". — str, May 12 '19 at 18:30

score 7 · Accepted Answer · answered May 12 '19 at 18:27

7

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

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

MongoPlayground

answered May 12 '19 at 18:27

Ashh

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How to find length of the array mongodb

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