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I have three documents that looks like this:

_id: ObjectId('61e1312ad435c7124aa883a1')
name: "Brian"
languages: "English,Spanish,French"

_id: ObjectId('52e1312ad435c7124aa883a2')
name: "Max"
languages: "English"

_id: ObjectId('37e1312ad435c7124aa883a9')
name: "Mike"
languages: ""

As you can see, the languages field can either be empty, have one item, or multiple items separated by commas.

How can I turn the languages field into an Array? The end result should look like this:

_id: ObjectId('61e1312ad435c7124aa883a1')
name: "Brian"
languages: [
    "English",
    "Spanish",
    "French"
]

_id: ObjectId('52e1312ad435c7124aa883a2')
name: "Max"
languages: [
    "English"
]

_id: ObjectId('37e1312ad435c7124aa883a9')
name: "Mike"
languages: []
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  • Update/Aggregate? Commented Jun 13, 2022 at 12:52
  • Not sure what you mean? Commented Jun 13, 2022 at 13:00

1 Answer 1

Reset to default
1

You can use $split to do this, like so:

db.collection.aggregate([
  {
    $addFields: {
      "languages": {
        $filter: {
          input: {
            $split: [
              "$languages",
              ","
            ]
          },
          cond: {
            $gt: [
              {
                $strLenCP: "$$this"
              },
              0
            ]
          }
        }
      }
    }
  }
])

Mongo Playground

If you want to update the entire collection you can use the same pipelined within an update with the "pipelined update" syntax:

db.collection.updateMany(
{},
[
  {
    "$set": {
      "languages": {
        $filter: {
          input: {
            $split: [
              "$languages",
              ","
            ]
          },
          cond: {
            $gt: [
              {
                $strLenCP: "$$this"
              },
              0
            ]
          }
        }
      }
    }
  }
])
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