Examples with OpBGP org.apache.jena.sparql.algebra.op.OpBGP used on opensource projects

Example 11 with OpBGP

use of org.apache.jena.sparql.algebra.op.OpBGP in project jena by apache.

the class TransformMergeBGPs method transform.

@Override
public Op transform(OpJoin opJoin, Op left, Op right) {
    BasicPattern p1 = asBGP(left);
    BasicPattern p2 = asBGP(right);
    if (p1 != null && p2 != null) {
        BasicPattern p = merge(p1, p2);
        return new OpBGP(p);
    }
    return super.transform(opJoin, left, right);
}

Example 12 with OpBGP

use of org.apache.jena.sparql.algebra.op.OpBGP in project jena by apache.

the class LibSDB method findTriples.

/** Find triples, in the default graph or a named graph. */
public static Iterator<Triple> findTriples(DatasetGraph dsg, Node g, Node s, Node p, Node o) {
    if (Var.isVar(g))
        throw new InternalErrorException("Graph node is a variable : " + g);
    final Node vs = varOrConst(s, "s");
    final Node vp = varOrConst(p, "p");
    final Node vo = varOrConst(o, "o");
    // Evaluate as an algebra expression
    Triple triple = new Triple(vs, vp, vo);
    BasicPattern pattern = new BasicPattern();
    pattern.add(triple);
    Op op = (g != null) ? new OpQuadPattern(g, pattern) : new OpBGP(pattern);
    Plan plan = QueryEngineSDB.getFactory().create(op, dsg, BindingRoot.create(), null);
    QueryIterator qIter = plan.iterator();
    Iterator<Binding> iter;
    if (SDB.getContext().isTrue(SDB.streamGraphAPI)) {
        // Assumes iterator closed properly.
        iter = qIter;
    } else {
        // ---- Safe version: 
        List<Binding> x = Iter.toList(qIter);
        Iterator<Binding> qIter2 = x.iterator();
        qIter.close();
        iter = qIter2;
    }
    return Iter.map(iter, (b) -> bindingToTriple(vs, vp, vo, b));
}

Example 13 with OpBGP

use of org.apache.jena.sparql.algebra.op.OpBGP 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 14 with OpBGP

use of org.apache.jena.sparql.algebra.op.OpBGP 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 = ResultSetStream.create(varNames, m, qIter);
        ResultSetFormatter.out(rs);
        qIter.close();
    }
    System.exit(0);
}

Example 15 with OpBGP

use of org.apache.jena.sparql.algebra.op.OpBGP in project jena by apache.

the class labelSearch method exec.

/* This be called once, with unevaluated arguments.
     * To do a rewrite of part of a query, we must use the fundamental PropertyFunction
     * interface to be called once with the input iterator.
     * Must not return null nor throw an exception.  Instead, return a QueryIterNullIterator
     * indicating no matches.  
     */
@Override
public QueryIterator exec(QueryIterator input, PropFuncArg argSubject, Node predicate, PropFuncArg argObject, ExecutionContext execCxt) {
    // No real need to check the pattern arguments because
    // the replacement triple pattern and regex will cope
    // but we illustrate testing here.
    Node nodeVar = argSubject.getArg();
    String pattern = NodeUtils.stringLiteral(argObject.getArg());
    if (pattern == null) {
        Log.warn(this, "Pattern must be a plain literal or xsd:string: " + argObject.getArg());
        return QueryIterNullIterator.create(execCxt);
    }
    if (false)
        // Old (ARQ 1) way - not recommended.
        return buildSyntax(input, nodeVar, pattern, execCxt);
    // Better
    // Build a SPARQL algebra expression
    // Hidden variable
    Var var2 = createNewVar();
    BasicPattern bp = new BasicPattern();
    Triple t = new Triple(nodeVar, RDFS.label.asNode(), var2);
    bp.add(t);
    OpBGP op = new OpBGP(bp);
    Expr regex = new E_Regex(new ExprVar(var2.getName()), pattern, "i");
    Op filter = OpFilter.filter(regex, op);
    // ---- Evaluation
    if (true) {
        // Use the reference query engine
        // Create a table for the input stream (so it uses working memory at this point,
        // which is why this is not the preferred way).
        // Then join to expression for this stage.
        Table table = TableFactory.create(input);
        Op op2 = OpJoin.create(OpTable.create(table), filter);
        return Algebra.exec(op2, execCxt.getDataset());
    }
    // Use the default, optimizing query engine.
    return QC.execute(filter, input, execCxt);
}