How to add filters to MongoDB query?

[GabrielSalernoILARI]

On the website and help sections of redash, it says you have to project a column with the "::filter" keyword added to the end, like this:

{
	"collection": "zipcodes",
	"aggregate": [{
		"$project": {
			"_id": "$_id",
			"city": "$city",
			"loc": "$loc",
			"pop": "$pop",
			"state::filter": "$state"
		}
	}]
}

Well I have 2 problems: when trying to do this with a new column generated with count ($sum), not only does the filter section not appear in the result, but the whole column disappears:

{
    "collection": "DATABASE_NORMALIZZATO",
    "fields": {
        "_id": 1,
        "TotalProducts": 1
    },
    "aggregate": [
        {
            "$group": {
                "_id": "$COSTRUTTORE | TITOLARE",
                "TotalProducts": {
                    "$sum": 1
                }
            }
        },
        {
            "$project": {
                "TotalProducts::filter": "$TotalProducts"
            }
        },
        {
            "$sort": [
                {
                    "name": "TotalProducts",
                    "direction": -1
                }
            ]
        }
    ]
}

here when adding ::filter to TotalProducts under $project the column (that would otherwise appear and work normally) is not present in the table at all.

The other issue I've found is when trying the filtering without "fields":

{
    "collection": "DATABASE_NORMALIZZATO",
    "aggregate":[{
        "$project":{
            "_id":"$_id",
            "DESCRIZIONE AREA::filter":"$DESCRIZIONE AREA",
            "DESCRIZIONE BENE DA OSPEDALE":"$DESCRIZIONE BENE DA OSPEDALE"
        }
    }]
}

here the filter section appears, but without using "fields", there are duplicates of both the filters and columns. i.e. instead of having 2 columns, DESCRIZIONE AREA and DESCRIZIONE BENE DA OSPEDALE, i have n*2 columns and n filters, where n is the number of rows found in the database (in my case 40 for testing). To avoid this you should use fields as far as I know but doing that simply doesn't show the filters nor the filtered column.