rdf_db:rdf_statistics/1

Obtain statistics on the RDF database. Defined statistics are:

graphs(-Count): Number of named graphs.
triples(-Count): Total number of triples in the database. This is the number of asserted triples minus the number of retracted ones. The number of visible triples in a particular context may be different due to visibility rules defined by the logical update view and transaction isolation.
resources(-Count): Number of resources that appear as subject or object in a triple. See rdf_resource/1.
properties(-Count): Number of current predicates. See rdf_current_predicate/1.
literals(-Count): Number of current literals. See rdf_current_literal/1.
gc(GCCount, ReclaimedTriples, ReindexedTriples, Time): Information about the garbage collector.
searched_nodes(-Count): Number of nodes expanded by rdf_reachable/3 and rdf_reachable/5.
lookup(rdf(S,P,O,G),Count): Number of queries that have been performed for this particular instantiation pattern. Each of S,P,O,G is either + or -. Fails in case the number of performed queries is zero.
hash_quality(rdf(S,P,O,G),Buckets,Quality,PendingResize): Statistics on the index for this pattern. Indices are created lazily on the first relevant query.
triples_by_graph(Graph, Count): This statistics is produced for each named graph. See triples for the interpretation of this value.