Persisting User Preferences - Relational or Document-Oriented Database

Question

I am looking into persisting user preferences past session expiration for an application and was curious if based on people's previous experiences a Relational Database (i.e. Oracle, MySql) or Document-Oriented Database (i.e. MongoDB, Redis) is better suited for this task. To help clarify the meaning of user preferences, my web-application would be storing pretty detailed information on a per-user basis including but not limited to: window size and position, grid column width and order, various widget states (collapsed/un-collapsed panels). All persistence in my application is currently handled by a Relational Database, but I have a feeling that something like user preferences may lend itself better to a Document-Oriented Database because it may be hard to represent this data in a strictly-structured way and a semi-structured approach may be better.

Answer 1

If you are already using a relational database for your application, it makes little sense to separate out just user privileges to a document-oriented db - it would just increase complexity. Starting a new app, it's worth considering.

For existing application you may consider using semi-structured data stores, like Postgresql's hstore.

Answer 2

The question being asked is Suitability not Practicality of installing new DB.

What is DB better suited for non-relational data like user preference ?

Clearly the answer should be non-relational DB. Document oriented NoSQL databases are suitable to storing these.

The OP mentioned Widgets etc preferences which are most likely JSON a document/objects. This is another reason mongoDB or JSON document oriented DB is more suitable.

There is also a fear of "installing new database" which is coming from the experience/pains of older relational databases which none of these NoSQL will have. But all this is besides the "suitability" question. Many factors will go into the "practicality" decision besides just the dependency.