public CloseableIteration<BindingSet, QueryEvaluationException> evaluate(final TupleExpr expr, final BindingSet bindings) throws QueryEvaluationException {
String db_type = configurationService.getStringConfiguration("database.type","h2");
SQLDialect dialect = null;
if(db_type.equals("h2")) {
dialect = SQLDialect.H2;
} else if(db_type.equals("postgres")) {
dialect = SQLDialect.POSTGRES;
} else if(db_type.equals("oracle")) {