поиск дубликатов записей mongo

mongo find duplicates by SN

//mongo find duplicates by SN
var duplicates = [];
db.devices.aggregate([
  { $match: { 
    name: { "$ne": '' }  // discard selection criteria
  }},
  { $group: { 
    _id: { name: "$_deviceId._SerialNumber"}, // can be grouped on multiple properties 
    dups: { "$addToSet": {
        _id: "$_id",
        _ProductClass: "$_deviceId._ProductClass",
        _Serial: "$_deviceId._SerialNumber"
        
    }},
    count: { "$sum": 1 } 
  }}, 
  { $match: { 
    count: { "$gt": 1 }    // Duplicates considered as count greater than one
  }}
],
{allowDiskUse: true}       // For faster processing if set is larger
)
.forEach(function(doc) {
    doc.dups.shift();      // First element skipped for deleting
    doc.dups.forEach( function(dupId){
        if (dupId._ProductClass === "OT2800") {
             duplicates.push(dupId._id);
            //console.log(dupId._id)
        }
        // duplicates.push(dupId); 
        }
    )    
})

console.log(duplicates.length)
printjson(duplicates); 
//db.devices.deleteOne({_id:{$in:duplicates}})