Consuming and Querying data

So what service should I use? My first thoughts were to push data to a SQL database, then I thought of Solr. Solr is fast and efficient, it's great for powerful full-text and faceted search, hit highlighting and rich document (e.g., Word, PDF) handling. So I pushed OpenURL Context Objects from DSpace to Solr and used simple queries to view the captured activity data.

Then I thought again. What data do I want returned from a recommendation service? I just want a few item handles and some metadata as suggestions to view alongside the current resource. I found I could do this using an SQL query on a test database but wasn't sure if I could construct queries with inner joins using Solr. I'm not that familiar with Solr and couldn't find what I wanted. A patch was available for the latest release that could do this but then again, maybe this isn't one of Solr's strengths ..or maybe I don't have the right data structure.

My thoughts turned back to basing a service on a SQL database.