/*
* 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.Comparator ;
import java.util.Iterator ;
import java.util.List ;
import org.apache.jena.atlas.data.BagFactory ;
import org.apache.jena.atlas.data.SortedDataBag ;
import org.apache.jena.atlas.data.ThresholdPolicy ;
import org.apache.jena.atlas.data.ThresholdPolicyFactory ;
import org.apache.jena.atlas.iterator.IteratorDelayedInitialization ;
import org.apache.jena.atlas.lib.Closeable ;
import org.openjena.riot.SerializationFactoryFinder ;
import com.hp.hpl.jena.query.QueryCancelledException ;
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 ;
/**
* Sort a query iterator. The sort will happen in-memory unless the size of the
* iterator exceeds a configurable threshold. In that case, a disk sort is used.
*
* @see SortedDataBag
*/
public class QueryIterSort extends QueryIterPlainWrapper
{
private final QueryIterator embeddedIterator; // Keep a record of the underlying source for .cancel.
final SortedDataBag<Binding> db;
public QueryIterSort(QueryIterator qIter, List<SortCondition> conditions, ExecutionContext context)
{
this(qIter, new BindingComparator(conditions, context), context) ;
}
public QueryIterSort(final QueryIterator qIter, final Comparator<Binding> comparator, final ExecutionContext context)
{
super(null, context) ;
this.embeddedIterator = qIter ;
ThresholdPolicy<Binding> policy = ThresholdPolicyFactory.policyFromContext(context.getContext());
this.db = BagFactory.newSortedBag(policy, SerializationFactoryFinder.bindingSerializationFactory(), comparator);
this.setIterator(new SortedBindingIterator(qIter));
}
@Override
public void requestCancel()
{
this.embeddedIterator.cancel() ;
super.requestCancel() ;
}
private class SortedBindingIterator extends IteratorDelayedInitialization<Binding> implements Closeable
{
private final QueryIterator qIter;
public SortedBindingIterator(final QueryIterator qIter)
{
this.qIter = qIter;
}
@Override
protected Iterator<Binding> initializeIterator()
{
try
{
db.addAll(qIter);
}
// Should we catch other exceptions too? Theoretically the user should be using this
// iterator in a try/finally block, and thus will call close() themselves.
catch (QueryCancelledException e)
{
close();
throw e;
}
return db.iterator();
}
@Override
public void close()
{
db.close();
}
}
}