That said. The issue with document oriented databases is that it is very difficult to get results based on referential info. Lets say you’re building a social network application and want to get the unread messages of all contacts living in the UK and are working at a company that is member of your partner program. This needs to filter on a combination of 3 documents `message`, `contact` and `company`. This can’t be done with CouchDB (and probably not with any other key/value store), because it can’t combine indexes from different documents. This makes the cases where you can actually use these type of databases very limited.

If EAV really seems like what you need, you should use something like CouchDB, Apache Cassandra , Project Voldemort, or one of the other emerging key/value storage technology.

By using EAV, you’ve already sacrificed any benefit using an RDBMS might have given you, so why are you still using an RDBMS?

I don’t mean to be cranky, but this is really one of those square-peg-in-a-round-hole situations.