How to update fields that are a string to an array with the string mongodb

Question

At some point data was saved as a string instead of an array of strings. There are some records that now have a value of:

users: "[email protected]"

but it should be:

users: ["[email protected]"]

Is there a way to update this in MongoDB?

Something like is what is a start, but I don't want to lose the data in the field. I need that info still, just inside an array:

db.users.update({users: {$type: 2}, {$set: {users: {$type: 4}})

mickl · Accepted Answer · 2019-06-13 05:51:14Z

2

You can use $out to modify existing collection:

db.collection.aggregate([
    {
        $addFields: {
            users: { $cond: [ { $eq: [ { $type: "$users" }, "string" ] }, [ "$users" ], "$users" ] }
        }
    },
    {
        $out: "collection"
    }
])

edited Jun 13, 2019 at 5:51

answered Jun 13, 2019 at 4:28

mickl

50.1k9 gold badges71 silver badges99 bronze badges

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

6 Comments

Plancke Over a year ago

Note that this solution will turn fields that already contain an array into an array within an array

mickl Over a year ago

@Plancke you are absolutely right, modified my answer, thank you !

Plancke Over a year ago

I think the updated answer might still do it for every record, I could be wrong but the $type operator on array fields matches any element inside the array. I don't have access to a mongo install to confirm this right now though. Could possibly do {"$users.0": {$exists: false}} to check if there's an element at index 0?

mickl Over a year ago

@Plancke please take a look here: mongoplayground.net/p/mFxdneyWc1u

Plancke Over a year ago

Ah, interesting, I recalled a few instances giving me troubles before using types with array, glad it works like this.

|

Collectives™ on Stack Overflow

How to update fields that are a string to an array with the string mongodb

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related