Order of responses to MongoDB $in query?

Question

The MongoDB docs on the $in conditional operator don't say anything about order. If I run a query of the form

db.things.find({'_id': {'$in': id_array}});

what will be the order of the returned results? And is there a way for me to tell MongoDB "I want the results sorted so that they're in the same order as the ids in id_array?"

Answer 1

the order of the results isn't mentioned because they won't be ordered in any dependable way. the only way to get them ordered would be to do separate queries client-side for each item in the $in array