MongoDB: Sort by array index

Question

I have a document with an array field that contains a list of values and I would like to sort by the first element in the array.

{
   field1 : "bla",
   field2 : "bla",
   field3 : "bla",
   someArray : [123, 456, 789]
}

I was trying to query like this:

db.testCollection.find({}).sort({"someArray[0]" : 1})

But this does not seem to have any effect and the sort gets ignored.

Is there any way this can be done?

Answer 1

Yes, the way to sort your collection by the first element of someArray in increasing order is:

db.testCollection.find().sort({"someArray.0": 1})

There is no need for the aggregation framework here. You were very close!