Remove default sorting value {"_id": 1}

[Bossa573]

my database contains a collection with index {"my_key": 1}

if I run the query :

{"my_key": "some_value"}

and leave the sorting value as empty, the query will become

db.myCollection.find({"my_key": "some_value"}).sort({ "_id": 1}).skip(0).limit(30)

and the database will perform a FULL db scan as there's no suitable index for this query

Here is the quote from mongodb support email sent by us about this issue:

Please note, the "_id" field is a line reference number, not  an actual _id