MongoDB Duplicate Documents even after adding unique key

php mongodb mongodb-query aggregation-framework

PHP Snippet 1:

db.yourCollection.aggregate([
    { "$group": {
        "_id": { "yourDuplicateKey": "$yourDuplicateKey" },
        "dups": { "$push": "$_id" },
        "count": { "$sum": 1 }
    }},
    { "$match": { "count": { "$gt": 1 } }}
]).forEach(function(doc) {
    doc.dups.shift();
    db.yourCollection.remove({ "_id": {"$in": doc.dups }});
});

PHP Snippet 2:

    $DataForDB = array( "AdmissionNo" => $admissionNo, 
    "StudentName" => $StudentName, "ParentName" => $ParentName);
    if(empty($Coll->findOne(array("StudenName" => $StudentName, "ParentName" => $ParentName)))){
    $Coll->insertOne($DataForDB);
    }

PHP Snippet 3:

 db.yourCollection.aggregate([
{ "$group": {
    "_id": { "yourDuplicateKey": "$yourDuplicateKey" },
    "dups": { "$push": "$_id" },
    "count": { "$sum": 1 }
}},
{ "$match": { "count": { "$gt": 1 } }}
], { allowDiskUse: true } )
.forEach(function(doc) {
    doc.dups.shift();
    db.yourCollection.remove({ "_id": {"$in": doc.dups }});
});