How to clean an array from empty objects in mongodb?

Question

Afterwards an aggregation in mongodb I get this results:

[
  my_arr:[
    {
      id: ObjectId('618f7ef057c2923be10d1111')
      //other stuff
    },
    {},
    {},
  ]
]

Is there a way to remove the empty object directly in the aggregation? or it is necessary to do it server side? I get that after doing an unwind and a group.

J.F. · Accepted Answer · 2021-11-27 19:28:07Z

2

You can add a new aggregation stage ( $project, $set or $addFields) with $filter like this:

{
  "$project": {
    "my_arr": {
      "$filter": {
        "input": "$my_arr",
        "as": "a",
        "cond": {
          "$ne": [
            "$$a",
            {}
          ]
        }
      }
    }
  }
}

This filter get only objects into the array where the object itself is not empty (i.e. is not {})

Example here

Also $set example and $addFields example

Also, you can use $$this to refer the object instead of value from as. Example here

edited Nov 27, 2021 at 19:28

answered Nov 27, 2021 at 18:56

J.F.

15.3k10 gold badges41 silver badges74 bronze badges

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

Collectives™ on Stack Overflow

How to clean an array from empty objects in mongodb?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related