/*
* 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 com.hp.hpl.jena.sparql.engine.iterator ;
import java.util.ArrayList ;
import java.util.Comparator ;
import java.util.Iterator ;
import java.util.NoSuchElementException ;
import org.openjena.atlas.data.BagFactory ;
import org.openjena.atlas.data.DistinctDataNet ;
import org.openjena.atlas.data.ThresholdPolicy ;
import org.openjena.atlas.data.ThresholdPolicyFactory ;
import org.openjena.atlas.iterator.Iter ;
import org.openjena.riot.SerializationFactoryFinder ;
import com.hp.hpl.jena.query.SortCondition ;
import com.hp.hpl.jena.sparql.engine.ExecutionContext ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.engine.binding.BindingComparator ;
import com.hp.hpl.jena.util.iterator.NiceIterator ;
/**
* A QueryIterator that suppresses items already seen. This will stream results
* until the spill to disk threshold is passed. At that point, it will not
* return any results until the input iterator has been exhausted.
*
* @see DistinctDataNet
*/
public class QueryIterDistinct extends QueryIter
{
private final QueryIterator inputIterator ;
final DistinctDataNet<Binding> db ;
boolean initialized = false ;
boolean finished = false ;
Binding slot ;
Iterator<Binding> dbIter ;
public QueryIterDistinct(QueryIterator qIter, ExecutionContext context)
{
super(context) ;
this.inputIterator = qIter ;
ThresholdPolicy<Binding> policy = ThresholdPolicyFactory.policyFromContext(context.getContext()) ;
Comparator<Binding> comparator = new BindingComparator(new ArrayList<SortCondition>(), context) ;
this.db = BagFactory.newDistinctNet(policy, SerializationFactoryFinder.bindingSerializationFactory(), comparator) ;
}
@Override
public void requestCancel()
{
inputIterator.cancel() ;
}
private void init()
{
if ( !initialized )
{
fill() ;
initialized = true ;
}
}
private void fill()
{
while ( inputIterator.hasNext() )
{
slot = inputIterator.next() ;
if ( db.netAdd(slot) )
{
return ;
}
}
if ( null == dbIter )
{
dbIter = db.netIterator() ;
}
if ( dbIter.hasNext() )
{
slot = dbIter.next() ;
return ;
}
close() ;
}
@Override
protected boolean hasNextBinding()
{
init() ;
return !finished ;
}
@Override
protected Binding moveToNextBinding()
{
if ( finished )
throw new NoSuchElementException() ;
init() ;
Binding toReturn = slot ;
fill() ;
return toReturn ;
}
@Override
protected void closeIterator()
{
if ( inputIterator != null )
{
NiceIterator.close(inputIterator) ;
// In case we wrapped, for example, another QueryIterator.
Iter.close(inputIterator) ;
}
if ( dbIter != null )
{
Iter.close(dbIter) ;
}
finished = true ;
slot = null ;
dbIter = null ;
db.close() ;
}
}