[cturner]

Seeking nosql advice. I'd like a system that allowed for standing queries instead of synchronous queries.

With mongo, if you want to know if something has changed, you send in a query.

I'd like to have a client subscribed to the db. Essentially, it's saying, "Whenever you get a dictionary that matches this query, send it through to me." It would hold this subscription over a standing socket connection.

Does anyone know of a system like this?

[arethuza]

CouchDB has a changes API that can send notifications to a client of what has changed - you can restrict this to changes you are interested in by using filter functions, which are a bit like views.

See: http://guide.couchdb.org/editions/1/en/notifications.html

[NB I can't really compare this to any other NoSQL db - I've only used CouchDB, although in the past I have built various document oriented data stored, something that I've now stopped doing!].