mongo删除重复数据保留一条

db.xxx.aggregate([
    {
        $group: { _id: {barcode: '$barcode', device_code: '$device_code'}, count: {$sum: 1},dups: {$addToSet: '$_id'}}
    },
    {
        $match: {count: {$gt: 1}}
    }
],
{allowDiskUse: true}
).forEach(function(doc){
    doc.dups.shift();
    db.xxx.remove({_id: {$in: doc.dups}});
})