Hello

As the order of criteria fields matters: http://docs.mongodb.org/manual/core/index-compound/#prefixes

I was wondering why not always sort the fields by key_name before creating indexes and searching?

i.e.

db.my_collection.ensure_index(b: 1, c: 1, a: 1)
=> internally could be replaced by db.my_collection.ensure_index(a: 1, b: 1, c: 1)

db.my_collection.find(c: 'c', b: 'b', a: 'a')
=> internally could be replaced by db.my_collection.find(a: 'a', b: 'b', c: 'c')

I think it could help to match the indexes easier, especially in cases we add the criteria fields based on user filter selections (complex views).

Does that make sense?

Thanks