what is a collection scan in mongodb?

Question

I'm aware what a "full collection scan" is. But i'm a little unsure if the term "collection scan" applies to queries that use B-tree cursor. Do queries that use a cursor other than the basic cursor perform a collection scan?

Answer 1

The short answer is the two terms are the same, or rather there is only "full collection scan".

If your query is using a B-tree cursor it is by definition not scanning the collection put is traversing the index in order to find the queried documents.

A collection scan occurs where no index can satisfy the query and we have to scan the full collection in order to find the required documents. See the link for all the information.

http://docs.mongodb.org/manual/reference/method/cursor.explain/