Java QueryIterator类代码示例

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Override
public QueryIterator exec(Binding binding, PropFuncArg argSubject,
		Node predicate, PropFuncArg argObject, ExecutionContext execCxt) {

	argSubject = Substitute.substitute(argSubject, binding);
	argObject = Substitute.substitute(argObject, binding);
	
	if(!argObject.getArg().isVariable()) {
		throw new ExprEvalException("Right hand side of tosh:targetContains must be a variable");
	}
	
	Node targetNode = argSubject.getArgList().get(0);
	Node shapesGraphNode = argSubject.getArgList().get(1);
	
	Model currentModel = ModelFactory.createModelForGraph(execCxt.getActiveGraph());
	Dataset dataset = new DatasetWithDifferentDefaultModel(currentModel, DatasetImpl.wrap(execCxt.getDataset()));

	Model model = dataset.getNamedModel(shapesGraphNode.getURI());
	Resource target = (Resource) model.asRDFNode(targetNode);

	Set<Node> focusNodes = new HashSet<Node>();
	SHACLUtil.addNodesInTarget(target, dataset, focusNodes);
	return new QueryIterExtendByVar(binding, (Var) argObject.getArg(), focusNodes.iterator(), execCxt);
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Override
public QueryIterator execEvaluated(Binding binding, Node subject, Node predicate, Node object, ExecutionContext execCxt) {
    Table table = getTable(predicate) ;
    if ( table == null ) {
        Log.warn(this,  "No table for "+SSE.str(predicate));
        return IterLib.noResults(execCxt) ;
    }
    
    if ( subject.isVariable() ) {
        if ( object.isVariable() )
            return execVarVar(binding, table, subject, object, execCxt) ;
        else
            return execVarTerm(binding, table, subject, object, execCxt) ;
    } else {
        if ( object.isVariable() )
            return execTermVar(binding, table, subject, object, execCxt) ;
        else
            return execTermTerm(binding, table, subject, object, execCxt) ;
    }
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Override
protected QueryIterator execute(OpFilter opFilter, QueryIterator input)
{
    if ( !isForLDF)
        return super.execute(opFilter, input) ;

    // If the filter does not apply to the input??
    // Where does ARQ catch this?

    // (filter (bgp ...))
    if ( OpBGP.isBGP(opFilter.getSubOp()) )
    {
        // Still may be a LDF graph in a non-LDF dataset (e.g. a named model)
        LinkedDataFragmentGraph graph = (LinkedDataFragmentGraph)execCxt.getActiveGraph() ;
        OpBGP opBGP = (OpBGP)opFilter.getSubOp() ;
        return executeBGP(graph, opBGP, input, opFilter.getExprs(), execCxt) ;
    }

    // (filter (anything else))
    return super.execute(opFilter, input) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
/** Execute without modification of the op - does <b>not</b> apply special graph name translations */
private static QueryIterator plainExecute(Op op, QueryIterator input, ExecutionContext execCxt)
{
    // -- Execute
    // Switch to a non-reordering executor
    // The Op may be a sequence due to TransformFilterPlacement
    // so we need to do a full execution step, not go straight to the SolverLib.

    ExecutionContext ec2 = new ExecutionContext(execCxt) ;
    ec2.setExecutor(plainFactory) ;

    // Solve without going through this executor again.
    // There would be issues of nested patterns but this is only a
    // (filter (bgp...)) or (filter (quadpattern ...)) or sequences of these.
    // so there are no nested patterns to reorder.
    return QC.execute(op, input, ec2) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
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) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
private QueryIterator execFixedSubject(Node nodeURI, Node nodeLocalname, Binding binding, ExecutionContext execCxt)
{
    if ( ! nodeURI.isURI() )
        // Subject bound but not a URI
        return QueryIterNullIterator.create(execCxt) ;

    // Subject is bound and a URI - get the localname as a Node 
    Node localname = NodeFactory.createLiteral(nodeURI.getLocalName()) ;
    
    // Object - unbound variable or a value? 
    if ( ! nodeLocalname.isVariable() )
    {
        // Object bound or a query constant.  Is it the same as the calculated value?
        if ( nodeLocalname.equals(localname) )
            // Same
            return QueryIterSingleton.create(binding, execCxt) ;
        // No - different - no match.
        return QueryIterNullIterator.create(execCxt) ;
    }
    
    // Object unbound variable - assign the localname to it.
    return QueryIterSingleton.create(binding, Var.alloc(nodeLocalname), localname, execCxt) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
private QueryIterator execAllNodes(Var subjVar, Node nodeLocalname,  Binding input, ExecutionContext execCxt)
{
    if ( ! nodeLocalname.isVariable() )
    {
        if ( ! nodeLocalname.isLiteral() )
            // Not a variable, not a literal=> can't match
            return QueryIterNullIterator.create(execCxt) ;
    
        if( ! NodeUtils.isSimpleString(nodeLocalname) )
            return QueryIterNullIterator.create(execCxt) ;
    }
    
    //Set bindings = new HashSet() ;    // Use a Set if you want unique results. 
    List<Binding> bindings = new ArrayList<Binding>() ;   // Use a list if you want counting results. 
    Graph graph = execCxt.getActiveGraph() ;
    
    ExtendedIterator<Triple>iter = graph.find(Node.ANY, Node.ANY, Node.ANY) ;
    for ( ; iter.hasNext() ; )
    {
        Triple t = iter.next() ;
        slot(bindings, input, t.getSubject(),   subjVar, nodeLocalname) ;
        slot(bindings, input, t.getPredicate(), subjVar, nodeLocalname) ;
        slot(bindings, input, t.getObject(),    subjVar, nodeLocalname) ;
    }
    return new QueryIterPlainWrapper(bindings.iterator(), execCxt) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
public static void main(String []args)
{
    String s = "SELECT DISTINCT ?s { ?s ?p ?o }";
    
    // Parse
    Query query = QueryFactory.create(s) ;
    System.out.println(query) ;
    
    // Generate algebra
    Op op = Algebra.compile(query) ;
    op = Algebra.optimize(op) ;
    System.out.println(op) ;
    
    // Execute it.
    QueryIterator qIter = Algebra.exec(op, ExQuerySelect1.createModel()) ;
    
    // Results
    for ( ; qIter.hasNext() ; )
    {
        Binding b = qIter.nextBinding() ;
        System.out.println(b) ;
    }
    qIter.close() ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Override
public QueryIterator execute(BasicPattern pattern, 
                             QueryIterator input,
                             ExecutionContext execCxt)
{
    // Just want to pick out some BGPs (e.g. on a particualr graph)
    // Test ::  execCxt.getActiveGraph() 
    if ( ! ( execCxt.getActiveGraph() instanceof GraphBase ) )
        // Example: pass on up to the original StageGenerator if
        // not based on GraphBase (which most Graph implementations are). 
        return other.execute(pattern, input, execCxt) ;
    
    System.err.println("MyStageGenerator.compile:: triple patterns = "+pattern.size()) ;

    // Stream the triple matches together, one triple matcher at a time. 
    QueryIterator qIter = input ;
    for (Triple triple : pattern.getList())
        qIter = new QueryIterTriplePattern(qIter, triple, execCxt) ;
    return qIter ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Test
public void testMultipleParallelIterators() throws IOException {
	CSVOptions options = new CSVOptions();
	options.setColumnNamesInFirstRow(false);
	CSVTable table = new CSVTable(InputStreamSource.fromString("Alice,Smith\nBob,Cook"), options);
	List<Var> vars = vars("a", "b", "ROWNUM");
	Binding row1 = binding(vars, "\"Alice\"", "\"Smith\"", "1");
	Binding row2 = binding(vars, "\"Bob\"", "\"Cook\"", "2");
	QueryIterator it1 = table.iterator(null);
	assertEquals(row1, it1.next());
	QueryIterator it2 = table.iterator(null);
	QueryIterator it3 = table.iterator(null);
	assertEquals(row1, it2.next());
	assertEquals(row2, it1.next());
	it2.close();
	assertEquals(row1, it3.next());
	assertEquals(row2, it3.next());
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
/** One round of rule evaluation */
private static void eval1(Graph source, StreamTriple out, Rule rule) {
    BasicPattern pattern = BasicPattern.wrap(rule.getBody()) ;
    ExecutionContext execContext = new ExecutionContext(ARQ.getContext(), source, null, null) ; 
    // Create a chain of triple iterators.
    QueryIterator iter = match(source, pattern) ;
    iter.forEachRemaining(b->{
        Triple t = Substitute.substitute(rule.getHead(), b) ;
        if ( t.isConcrete() && ! source.contains(t) )
            out.triple(t);
    }) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
/** Evaluate a BGP : encapsulate for a better/different version */  
private static QueryIterator match(Graph source, BasicPattern pattern) {
    ExecutionContext execContext = new ExecutionContext(ARQ.getContext(), source, null, null) ; 
    // Create a chain of triple iterators.
    QueryIterator chain = QueryIterSingleton.create(BindingFactory.root(), execContext) ; 
    for (Triple triple : pattern)
        chain = new QueryIterTriplePattern(chain, triple, execContext) ;
    return chain ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
/** Execute a BGP (and filters) on a LDF graph, which may be in default storage or it may be a named graph */
private static QueryIterator executeBGP(LinkedDataFragmentGraph graph, OpBGP opBGP, QueryIterator input, ExprList exprs,
                                        ExecutionContext execCxt)
{
    // Execute a BGP on the real default graph
    return optimizeExecuteTriples(graph, input, opBGP.getPattern(), exprs, execCxt) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Override
public QueryIterator execEvaluated(Binding binding, Node nodeURI, Node predicate, Node nodeLocalname, ExecutionContext execCxt)
{
    if ( ! nodeURI.isVariable() )
        return execFixedSubject(nodeURI, nodeLocalname, binding, execCxt) ;
    else
        return execAllNodes(Var.alloc(nodeURI), nodeLocalname, binding, execCxt) ;
}
 

import org.apache.jena.sparql.engine.QueryIterator; //导入依赖的package包/类
@Override
public QueryIterator eval(Op op, DatasetGraph dsg, Binding initial, Context context)
{
    // Extension point: access possible to all the parameters for execution.
    // Be careful to deal with initial bindings.
    Transform transform = new MyTransform() ;
    op = Transformer.transform(transform, op) ;
    return super.eval(op, dsg, initial, context) ;
}