As detailed in this (http://stackoverflow.com/questions/14855629/create-in-query-with-a-limit-per-match) stack overflow issue, it would be very useful to have the ability to limit a $in query so that only a certain number of results are returned PER MATCH. So, for example, say you are querying against an image collection, where each document in the collection has a 'ownerGUID' attribute which points back to a corresponding document in a collection called 'users'. Doing a $in query with an array of user GUIDS could be be limited so that only 5 image documents PER item in the array would be returned.