Implement anonymous blank nodes
This merge request:
-
Changes the database format so we don't need to generate an UUIDv4 URN string for blank nodes. Blank nodes are inserted URI-less, and a
urn:bnode:$ROWID
scheme is used to access those. Not generating URN strings can provide significant improvements in insertion performance and database size when many blank nodes are used. -
Adds a
ANONYMOUS_BNODES
TrackerSparqlConnection flag, that implements the behavior of blank nodes as defined in the SPARQL 1.1 spec, since the database format can now accommodate both behaviors on the fly.