gistfile1.txt

db.threads.aggregate([
    {
        "$match": {
            "$text": {
                "$search": "modx"
            }
        }
    },
    {
        "$facet":{
            
            "count": [
                {
                    "$group": {_id: null, count: {$sum: 1}}
                }                
            ],
            "channelIDs": [
                {
                    "$group": {_id: "$ci"}
                }
            ] 
        }
    }
])

Result is:
{
    "count" : [
        {
            "_id" : null,
            "count" : 360.0
        }
    ],
    "channelIDs" : [
        {
            "_id" : ObjectId("60fdb9d0535ed8596df08b90")
        }
    ]
}

Can i have result in form 
{
    "count" : 360.0,
    "channelIDs" : [        
          ObjectId("60fdb9d0535ed8596df08b90"
    ]
}