Converting string to Array (Aggregate mongodb)

Question

Im getting random data from my database using the aggregate but apparently some of them have their genre values in string not in array, How can i convert those random data genre from string to array?

const book = await Book.aggregate([
       /* This is just for testing which books has genres in specific type
       { 
        $match: { genre: { $type: "string" } } 
       },
       */
 
      {   
        $sample: { size: 6 } 
      }
]);

sample data result(genres that are in type of string)

[
    {
        "_id": "62710ac63ad1bfc6d17030fe",
        "title": "Birth of a Theorem",
        "author": "Villani, Cedric",
        "genre": "mathematics",
        "publisher": "Bodley Head",
        "dateOfPublication": "2002-02-28T00:00:00.000Z",
        "noOfCopies": 16,
        "type": "Book",
        "form": "Non-fiction",
        "isbn": "979-81202-479229-867673-6",
        "dateAdded": "2002-11-28T00:00:00.000Z"
    },
    {
        "_id": "62710ac63ad1bfc6d1703108",
        "title": "All the President's Men",
        "author": "Woodward, Bob",
        "genre": "history",
        "publisher": "Random House",
        "dateOfPublication": "2018-02-19T00:00:00.000Z",
        "noOfCopies": 56,
        "type": "Book",
        "form": "Non-fiction",
        "isbn": "978-41428-6606587-937631-",
        "dateAdded": "2011-02-23T00:00:00.000Z"
    },
]

sample data result(genres that are in type of array)

[
    {
        "_id": "62710ac63ad1bfc6d17030be",
        "title": "Superfreakonomics",
        "author": "Dubner, Stephen",
        "genre": [
            "economics",
            "computer_science"
        ],
        "publisher": "HarperCollins",
        "dateOfPublication": "2003-10-06T00:00:00.000Z",
        "noOfCopies": 31,
        "type": "Thesis",
        "form": "Non-fiction",
        "isbn": "978-35029-7186192-465859-7",
        "dateAdded": "2009-02-12T00:00:00.000Z"
    }
]

YuTing · Accepted Answer · 2022-05-11 02:37:57Z

2

$sample is for documents instead of embedded array.

Update

db.collection.update({
  genre: {
    $type: "string"
  }
},
[
  {
    $set: { genre: [ "$genre" ] }
  }
],
{
  multi: true
})

mongoplayground

Aggregate

db.collection.aggregate([
  {
    $match: {
      genre: {
        $type: "string"
      }
    }
  },
  {
    $set: {
      genre: {
        $cond: {
          if: { $eq: [ { $type: "$genre" }, "string" ] },
          then: [ "$genre" ],
          else: "$genre"
        }
      }
    }
  }
])

mongoplayground

edited May 11, 2022 at 2:37

answered May 11, 2022 at 2:32

YuTing

6,6692 gold badges8 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

JAS MAL Over a year ago

Hello, I tried using the update method but i dont know where to put it because im using asynchandler when getting the random data from db, but the aggregate method that you put in your answer worked for me. Thank you!

Collectives™ on Stack Overflow

Converting string to Array (Aggregate mongodb)

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related