Identifying the null values in a Collection

[steevej (Steeve Juneau)]

Have you solve your other issue:

Update the Key in the nested array

If you look at the $map documentation, you will see it returns an array with the applied results By doing you explicitly ask to $set history.status to an array. So it is totally normal that Most likely you do not $set/$map the appropriate field. But since your sample input document is not formatted correctly we are not to cut-n-paste it to experiment.

If you did share the solution or mark one of the reply as the solution.

This following post also needs closure:

Update the key data type from string to int64

If you look at the $map documentation you will read the following about $$this: A name for the variable that represents each individual element of the input array. If no name is specified, the variable name defaults to this. In you sample document, the field fulfill is an array of objects. You $map using input:$fulfill and $toLong:$$this.tagSerialNumbers, but tagSerialNumbers is an array and this is why you get: But I already mentioned: An hint to the solution was also mentioned:

As mentioned in your other posts:

@steevej

Please read Formatting code and log snippets in posts and update your sample documents and pipeline so it is easier to understand and to cut-n-paste for experimentation.