CouchDB supports something called group_level in the view queries. On pcapr, we never really had the need to use this feature though we have over 52 different views. But in a recent internal project, we had the need to display folders in the application that can be expanded and collapsed. Each document in CouchDB represents a file of sorts and contains the relative path name. One of the views in the app is a classic folder view that can be expanded recursively. Obviously, from a scaling perspective, we don’t want to load all this data up front and that’s exactly where the group_level comes in. This was my first time playing with this capability and I have to say, once you get grok this, it’s totally cool.
You can read more about CouchDB
group_level ☞ here and ☞ here.
Original title and link: CouchDB group_level for hierarchical data (NoSQL databases © myNoSQL)