How to store an ordered set of documents in MongoDB without using a capped collection

Question

What\'s a good way to store a set of documents in MongoDB where order is important? I need to easily insert documents at an arbitrary position and possibly reorder them lat

Answer 1

An _id field in MongoDB is a unique, indexed key similar to a primary key in relational databases. If there is an inherent order in your documents, ideally you should be able to associate a unique key to each document, with the key value reflecting the order. So while preparing your document for insertion, explicitly add an _id field as this key (if you do not, mongo creates it automatically with a BSON objectid).

As far as retrieving the results are concerned, MongoDB does not guarantee the order of return documents unless you explicitly use .sort() . If you do not use .sort(), the results are usually returned in natural order (order of insertion).Again, there is no guarantee on this behavior.

I'd advise you to override _id with your order while inserting, and use a sort while retrieving. Since _id is a necessary and auto-indexed entity, you will not be wasting any space defining a sort key, and storing the index for it.