In a project that we’ve just started, we are using OpenLink Virtuoso as a triple store. I encountered a frustrating bug when accessing it via the Jena Provider where submitting a SPARQL query with a top-level LIMIT clause would return one less result than expected. In my case, the first query I tried was an existential query with LIMIT 1, so it caused much head scratching as to why I was getting no results.
Luckily OpenLink are responsive to issues raised on GitHub, so once I raised this issue and created an example project, it was quickly found to be solved by using the latest version of their JDBC4 jar. Problem solved.