Examples with SingletonSet org.eclipse.rdf4j.query.algebra.SingletonSet used on opensource projects

Example 6 with SingletonSet

use of org.eclipse.rdf4j.query.algebra.SingletonSet in project rdf4j by eclipse.

the class TupleExprBuilder method visit.

@Override
public TupleExpr visit(ASTDescribe node, Object data) throws VisitorException {
    TupleExpr tupleExpr = (TupleExpr) data;
    if (tupleExpr == null) {
        tupleExpr = new SingletonSet();
    }
    Extension e = new Extension();
    ProjectionElemList projectionElements = new ProjectionElemList();
    for (int i = 0; i < node.jjtGetNumChildren(); i++) {
        ValueExpr resource = (ValueExpr) node.jjtGetChild(i).jjtAccept(this, null);
        if (resource instanceof Var) {
            projectionElements.addElement(new ProjectionElem(((Var) resource).getName()));
        } else {
            String alias = "_describe_" + UUID.randomUUID().toString().replaceAll("-", "_");
            ExtensionElem elem = new ExtensionElem(resource, alias);
            e.addElement(elem);
            projectionElements.addElement(new ProjectionElem(alias));
        }
    }
    if (!e.getElements().isEmpty()) {
        e.setArg(tupleExpr);
        tupleExpr = e;
    }
    Projection p = new Projection(tupleExpr, projectionElements);
    return new DescribeOperator(p);
}