Mongodb $lookup Not working with _id

Question

wend try with this query, return the lookup is empty

db.getCollection(\'tests\').aggregate([
    {$match: {typet:\'Req\'}},
    {$project: {incharge:1}},
            


        

Answer 1

try changing type of incharge which is string to ObjectId in aggregate function like this

{ 
    $project : {
        incharge : {
            $toObjectId : "$incharge"
        }
    }
}