Examples with Projection org.openrdf.query.algebra.Projection used on opensource projects

Example 76 with Projection

use of org.openrdf.query.algebra.Projection in project backstage by zepheira.

the class Expression method computeOutputOnValue.

public ExpressionQueryResult computeOutputOnValue(Value value, Database database, SailRepositoryConnection connection) throws ExpressionException {
    TupleQueryBuilder builder = new TupleQueryBuilder();
    Var valueVar = builder.makeVar("value", value);
    ExpressionResult expressionResult = computeOutputOnItem(database, builder, valueVar);
    if (expressionResult.valueExpr instanceof Var) {
        Var resultVar = (Var) expressionResult.valueExpr;
        ProjectionElemList projectionElements = new ProjectionElemList();
        projectionElements.addElement(new ProjectionElem(resultVar.getName()));
        TupleExpr t = builder.makeFilterTupleExpr();
        if (t == null) {
            // TODO[dfhuynh]: This happens if the expression is just "value". I'm not sure what to do here.
            return null;
        }
        Projection projection = new Projection(t, projectionElements);
        TupleQuery query = new MyTupleQuery(new ParsedTupleQuery(projection), connection);
        return new ExpressionQueryResult(query, expressionResult.valueType, resultVar);
    }
    return null;
}