how to flatten an array in mongodb?

Question

How to flatten an array in mongodb?

Name:[["abc","xvz"]]

into this way

Name:["abc","xyz"]

without using aggregate.

Aggregate will display the result but it shouldn't write the result back to the document.

Answer 1

Not sure why you don't want to use aggregation as this is a trivial step using [$unwind][2] . Here is a simple example. If you want to overwrite you could just use update with the results or send the output of aggregate to a new collection with [$out][2] .

Below is an example using the MongoDB Shell.

>
> use test
switched to db test
> db.test.insertOne({name:[['xyz','abc']]})
{
        "acknowledged" : true,
        "insertedId" : ObjectId("5dbc28bbefffaafb7d97d7f1")
}
> db.test.aggregate([{"$unwind" : "$name"}])
{ "_id" : ObjectId("5dbc28bbefffaafb7d97d7f1"), "name" : [ "xyz", "abc" ] }
>