/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.sparql.engine.main.iterator;
import java.util.Iterator ;
import java.util.NoSuchElementException ;
import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.atlas.iterator.SingletonIterator ;
import org.apache.jena.atlas.lib.Lib ;
import org.apache.jena.graph.Graph ;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.ARQInternalErrorException ;
import org.apache.jena.sparql.algebra.Op ;
import org.apache.jena.sparql.algebra.op.OpGraph ;
import org.apache.jena.sparql.core.DatasetGraph ;
import org.apache.jena.sparql.core.Quad ;
import org.apache.jena.sparql.core.Substitute ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.iterator.QueryIterAssignVarValue ;
import org.apache.jena.sparql.engine.iterator.QueryIterRepeatApply ;
import org.apache.jena.sparql.engine.iterator.QueryIterSingleton ;
import org.apache.jena.sparql.engine.iterator.QueryIterSub ;
import org.apache.jena.sparql.engine.main.QC ;
public class QueryIterGraph extends QueryIterRepeatApply
{
/*
* A note on the strange case of GRAPH ?g { ... ?g ... }
*
* The inner pattern is solved, then the outer ?g=... is added. This happens
* because the outer ?g is added by QueryIterAssignVarValue which tests a
* variable is the same as the binding and drops the binding if not. (which
* is a specialised form of join.
*/
protected OpGraph opGraph ;
public QueryIterGraph(QueryIterator input, OpGraph opGraph, ExecutionContext context)
{
super(input, context) ;
this.opGraph = opGraph ;
}
@Override
protected QueryIterator nextStage(Binding outerBinding) {
DatasetGraph ds = getExecContext().getDataset() ;
// Is this closed?
Iterator<Node> graphNameNodes = makeSources(ds, outerBinding, opGraph.getNode());
// List<Node> x = Iter.toList(graphNameNodes) ;
// graphNameNodes = x.iterator() ;
// System.out.println(x) ;
QueryIterator current = new QueryIterGraphInner(outerBinding, graphNameNodes, opGraph, getExecContext()) ;
return current ;
}
/** Bound value or null */
private static Node resolve(Binding b, Node n) {
if ( ! n.isVariable() ) return n ;
return b.get(Var.alloc(n)) ;
}
protected static Iterator<Node> makeSources(DatasetGraph data, Binding b, Node graphVar) {
Node n2 = resolve(b, graphVar) ;
if ( n2 != null && n2.isLiteral() )
// Blank node or literal possible after resolving
return Iter.nullIterator() ;
// n2 is a URI or null.
if ( n2 == null )
// Do all submodels.
return data.listGraphNodes() ;
return new SingletonIterator<>(n2) ;
}
protected static class QueryIterGraphInner extends QueryIterSub
{
protected final Binding parentBinding ;
protected final Iterator<Node> graphNames ;
protected final OpGraph opGraph ;
protected final Op opSubstituted ;
protected QueryIterGraphInner(Binding parent, Iterator<Node> graphNames, OpGraph opGraph, ExecutionContext execCxt) {
super(null, execCxt) ;
this.parentBinding = parent ;
this.graphNames = graphNames ;
this.opGraph = opGraph ;
this.opSubstituted = Substitute.substitute(opGraph.getSubOp(), parent) ;
}
@Override
protected boolean hasNextBinding() {
for ( ;; ) {
if ( iter == null )
iter = nextIterator();
if ( iter == null )
return false;
if ( iter.hasNext() )
return true;
iter.close();
iter = nextIterator();
if ( iter == null )
return false;
}
}
@Override
protected Binding moveToNextBinding() {
if ( iter == null )
throw new NoSuchElementException(Lib.className(this) + ".moveToNextBinding");
return iter.nextBinding();
}
// This code predates ARQ using Java 1.5.
// This is very like QueryIteratorRepeatApply except its not
// repeating over bindings, but over graph nodes.
// There is a tradeoff of generalising QueryIteratorRepeatApply to Objects
// and hence no type safety. Or duplicating code (generics?)
protected QueryIterator nextIterator() {
if ( ! graphNames.hasNext() )
return null ;
Node gn = graphNames.next() ;
QueryIterator qIter = buildIterator(parentBinding, gn, opSubstituted, getExecContext()) ;
if ( qIter == null )
// Know to be nothing (e.g. graph does not exist).
return null ;
if ( Var.isVar(opGraph.getNode()) ) {
// This is the join of the graph node variable to the sub-pattern solution.
// Do after the subpattern so that the variable is not visible to the
// subpattern.
Var v = Var.alloc(opGraph.getNode()) ;
qIter = new QueryIterAssignVarValue(qIter, v, gn, getExecContext()) ;
}
return qIter ;
}
// Create the iterator - or return null if there can't be any results.
protected static QueryIterator buildIterator(Binding binding, Node graphNode, Op opExec, ExecutionContext outerCxt) {
if ( !graphNode.isURI() && !graphNode.isBlank() )
// e.g. variable bound to a literal or blank node.
throw new ARQInternalErrorException("QueryIterGraphInner.buildIterator: Not a URI or balnk node: "+graphNode) ;
// We can't just use DatasetGraph.getGraph because it may
// "auto-create" graphs. Use the containsGraph function.
boolean syntheticGraph = ( Quad.isDefaultGraph(graphNode) || Quad.isUnionGraph(graphNode) ) ;
if ( ! syntheticGraph && ! outerCxt.getDataset().containsGraph(graphNode) )
return null ;
Graph g = outerCxt.getDataset().getGraph(graphNode) ;
// And the contains was true??!!!!!!
if ( g == null )
return null ;
//throw new ARQInternalErrorException(".containsGraph was true but .getGraph is null") ;
ExecutionContext cxt2 = new ExecutionContext(outerCxt, g) ;
QueryIterator subInput = QueryIterSingleton.create(binding, cxt2) ;
return QC.execute(opExec, subInput, cxt2) ;
}
@Override
protected void requestSubCancel()
{}
@Override
protected void closeSubIterator()
{}
}
}