There are a number of limitations in the current handling of Jena TDB graphs using the clerezza wrapper API that prevents scalable Sparql queries on large Jena backed triple collections on one hand and scalable support for named graphs in SPARQL on the other hand:
https://issues.apache.org/jira/browse/CLEREZZA-466 https://issues.apache.org/jira/browse/CLEREZZA-467 https://issues.apache.org/jira/browse/CLEREZZA-468 -- Olivier
