Examples with Expr org.apache.jena.sparql.expr.Expr used on opensource projects

Example 71 with Expr

use of org.apache.jena.sparql.expr.Expr in project jena by apache.

the class labelSearch method buildSyntax.

// Build SPARQL syntax and compile it.
// Not recommended.
private QueryIterator buildSyntax(QueryIterator input, Node nodeVar, String pattern, ExecutionContext execCxt) {
    Var var2 = createNewVar();
    // Triple patterns for   ?x rdfs:label ?hiddenVar
    ElementTriplesBlock elementBGP = new ElementTriplesBlock();
    Triple t = new Triple(nodeVar, RDFS.label.asNode(), var2);
    elementBGP.addTriple(t);
    // Regular expression for  regex(?hiddenVar, "pattern", "i") 
    Expr regex = new E_Regex(new ExprVar(var2.getName()), pattern, "i");
    ElementGroup elementGroup = new ElementGroup();
    elementGroup.addElement(elementBGP);
    elementGroup.addElement(new ElementFilter(regex));
    // Compile it.
    // The better design is to build the Op structure programmatically,
    Op op = Algebra.compile(elementGroup);
    op = Algebra.optimize(op, execCxt.getContext());
    return QC.execute(op, input, execCxt);
}

Example 72 with Expr

use of org.apache.jena.sparql.expr.Expr in project jena by apache.

the class AlgebraExec method main.

public static void main(String[] argv) {
    String BASE = "http://example/";
    BasicPattern bp = new BasicPattern();
    Var var_x = Var.alloc("x");
    Var var_z = Var.alloc("z");
    // ---- Build expression
    bp.add(new Triple(var_x, NodeFactory.createURI(BASE + "p"), var_z));
    Op op = new OpBGP(bp);
    //Expr expr = ExprUtils.parse("?z < 2 ") ;
    Expr expr = new E_LessThan(new ExprVar(var_z), NodeValue.makeNodeInteger(2));
    op = OpFilter.filter(expr, op);
    // ---- Example setup
    Model m = makeModel();
    m.write(System.out, "TTL");
    System.out.println("--------------");
    System.out.print(op);
    System.out.println("--------------");
    // ---- Execute expression
    QueryIterator qIter = Algebra.exec(op, m.getGraph());
    // -------- Either read the query iterator directly ...
    if (false) {
        for (; qIter.hasNext(); ) {
            Binding b = qIter.nextBinding();
            Node n = b.get(var_x);
            System.out.println(NodeFmtLib.displayStr(n));
            System.out.println(b);
        }
        qIter.close();
    } else {
        // -------- Or make ResultSet from it (but not both - reading an
        //          iterator consumes the current solution)
        List<String> varNames = new ArrayList<>();
        varNames.add("x");
        varNames.add("z");
        ResultSet rs = new ResultSetStream(varNames, m, qIter);
        ResultSetFormatter.out(rs);
        qIter.close();
    }
    System.exit(0);
}

Example 73 with Expr

use of org.apache.jena.sparql.expr.Expr in project jena by apache.

the class ExProg2 method main.

public static void main(String[] args) {
    Model model = createModel();
    Query query = QueryFactory.make();
    query.setQuerySelectType();
    // See also ExProg1
    ElementGroup elg = new ElementGroup();
    Var varTitle = Var.alloc("title");
    Var varX = Var.alloc("x");
    Triple t1 = new Triple(varX, DC.title.asNode(), varTitle);
    elg.addTriplePattern(t1);
    // Adds a filter.  Need to wrap variable in a NodeVar.
    Expr expr = new E_Regex(new ExprVar(varTitle), "sparql", "i");
    ElementFilter filter = new ElementFilter(expr);
    elg.addElementFilter(filter);
    // Attach the group to query.  
    query.setQueryPattern(elg);
    // Choose what we want - SELECT ?title
    query.addResultVar(varTitle);
    // Print query with line numbers
    // Prefix mapping just helps serialization
    query.getPrefixMapping().setNsPrefix("dc", DC.getURI());
    query.serialize(new IndentedWriter(System.out, true));
    System.out.println();
    try (QueryExecution qexec = QueryExecutionFactory.create(query, model)) {
        // Assumption: it's a SELECT query.
        ResultSet rs = qexec.execSelect();
        // The order of results is undefined.
        System.out.println("Titles: ");
        for (; rs.hasNext(); ) {
            QuerySolution rb = rs.nextSolution();
            // Get title - variable names do not include the '?' (or '$')
            RDFNode x = rb.get("title");
            // Check the type of the result value
            if (x instanceof Literal) {
                Literal titleStr = (Literal) x;
                System.out.println("    " + titleStr);
            } else
                System.out.println("Strange - not a literal: " + x);
        }
    }
}

Example 74 with Expr

use of org.apache.jena.sparql.expr.Expr in project jena by apache.

the class TransformFilterPlacementConservative method buildFilter.

/** Place expressions around an Op */
private static Op buildFilter(ExprList exprs, Op op) {
    if (exprs.isEmpty())
        return op;
    for (Iterator<Expr> iter = exprs.iterator(); iter.hasNext(); ) {
        Expr expr = iter.next();
        if (op == null)
            op = OpTable.unit();
        op = OpFilter.filter(expr, op);
        iter.remove();
    }
    return op;
}

Example 75 with Expr

use of org.apache.jena.sparql.expr.Expr in project jena by apache.

the class TransformFilterPlacement method wrapBGP.

/** Wrap the Basic Pattern with any applicable expressions from the ExprList
     * but do not break up the BasicPattern in any way.
     */
private Placement wrapBGP(ExprList exprsIn, BasicPattern pattern) {
    Set<Var> vs = new HashSet<>();
    VarUtils.addVars(vs, pattern);
    ExprList pushed = new ExprList();
    ExprList unpushed = new ExprList();
    for (Expr e : exprsIn) {
        Set<Var> eVars = e.getVarsMentioned();
        if (vs.containsAll(eVars))
            pushed.add(e);
        else
            unpushed.add(e);
    }
    // Can't push anything into a filter around this BGP
    if (pushed.size() == 0)
        return noChangePlacement;
    // Safe to place some conditions around the BGP
    Op opx = OpFilter.filterBy(pushed, new OpBGP(pattern));
    return result(opx, unpushed);
}