Trying to update embedded doc only when matching condition is true but its inserting even condition not seems true

Working with Data
1

Hi Team,

I am trying to update embedded doc only when matching condition is true but its inserting even condition not seems true. May be I am missing something here.

Sample mongo playground

I dont want to insert role if matching role is already there.

2

It is not clear if this issue is the same as

3

That I have done with aggregation pipeline. But here I was trying with simple update with elemmatch filter for another scenario and trying to understand why it’s not working in this case.

4

In case you still need some insight about this playground.

1 - if roles is null, $push will fail

mongosh> c.find( { _id : 1 })
{ _id: 1, roles: null }
mongosh> c.updateOne( { _id : 1 } , { "$push" : { "roles" : [ { _id : 101 , name : 201 }]}})
MongoServerError: The field 'roles' must be an array but is of type null in document {_id: 1}

Starting with 4.2 you could handle this case using a $set stage with $cond to replace roles:null with roles:[ ].

2 - I do not quite understand the purpose of

{  "$nor": [
        {
          "roles": {
            "$ne": null,
            "$not": { "$size": 0  }
          }
        }
      ]
    }
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