I'm looking for suggestions on a SPARQL performance issue. My test
model has ~800 sentences, and processing of one select query takes about
25 minutes. The query is a basic graph pattern with 9 variables and 20
triples, plus a filter that forces distinct variables to have distinct
solutions using pair-wise not-equals constraints. No option clause or
anything else fancy.
I am issuing the query against an inference model. Most of the asserted
sentences are in imported models. If I iterate over all the statements
in the OntModel, I get ~1500 almost instantly. I experimented with
several of the reasoners.
Below is the basic control flow. The thing I found curious is that the
execSelect() method finishes almost instantly. It is the iteration over
the ResultSet that is taking all the time, it seems in the call to
selectResult.hasNext(). The result has 192 rows, 9 columns. The results
are provided in bursts of 8 rows each, with ~1 minute between bursts.
OntModel ontologyModel = getMyOntModel(); // Tried various reasoners
String selectQuery = getMySelectQuery();
QueryExecution selectExec =
QueryExecutionFactory.create(selectQuery, ontologyModel);
ResultSet selectResult = selectExec.execSelect();
while (selectResult.hasNext()) { // Time seems to be spent in
hasNext
QuerySolution selectSolution = selectResult.next();
for (String var : getMyVariablesOfInterest() {
RDFNode varValue = selectSolution.get(var);
// process varValue
}
}
Any suggestions would be appreciated.
