/*
* 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.graph;
import org.apache.jena.atlas.data.DataBag ;
import org.apache.jena.atlas.data.ThresholdPolicy ;
import com.hp.hpl.jena.graph.Capabilities ;
import com.hp.hpl.jena.graph.Triple ;
import com.hp.hpl.jena.graph.TripleMatch ;
import com.hp.hpl.jena.graph.TripleMatchIterator ;
import com.hp.hpl.jena.graph.impl.TripleStore ;
import com.hp.hpl.jena.mem.GraphMemBase ;
import com.hp.hpl.jena.util.iterator.ExtendedIterator ;
/**
* A Graph based on top of a DataBag. This means it has some limitations:
* <ol>
* <li>Cannot add any triples after you call find() unless you first call clear() or getBulkUpdateHandler().removeAll().</li>
* <li>Cannot remove any triples except by calling clear() or getBulkUpdateHandler().removeAll().</li>
* <li>There is no indexing, so find() will always scan all triples.</li>
* <li>The size() method is not guaranteed to be accurate, treat it as an estimate.</li>
* <li>You must call close() in order to release any resources (such as spill files).</li>
* </ol>
*/
public abstract class GraphDataBag extends GraphMemBase
{
private final ThresholdPolicy<Triple> thresholdPolicy ;
private DataBag<Triple> db ;
public GraphDataBag(ThresholdPolicy<Triple> thresholdPolicy)
{
super() ;
this.thresholdPolicy = thresholdPolicy;
capabilities = new Capabilities()
{
@Override
public boolean sizeAccurate() { return false; }
@Override
public boolean addAllowed() { return addAllowed( false ); }
@Override
public boolean addAllowed( boolean every ) { return true; }
@Override
public boolean deleteAllowed() { return deleteAllowed( false ); }
@Override
public boolean deleteAllowed( boolean every ) { return false; }
@Override
public boolean canBeEmpty() { return true; }
@Override
public boolean iteratorRemoveAllowed() { return false; }
@Override
public boolean findContractSafe() { return true; }
@Override
public boolean handlesLiteralTyping() { return true; }
};
this.db = createDataBag();
}
protected abstract DataBag<Triple> createDataBag();
protected ThresholdPolicy<Triple> getThresholdPolicy()
{
return thresholdPolicy;
}
@Override
protected TripleStore createTripleStore()
{
// No TripleStore for us
return null ;
}
@Override
public void performAdd(Triple t)
{
db.add(t) ;
}
@Override
public int graphBaseSize()
{
return (int) db.size() ;
}
@Override
protected void destroy()
{
db.close() ;
}
@Override
public void clear()
{
db.close() ;
db = createDataBag() ;
}
@Override
protected ExtendedIterator<Triple> graphBaseFind(TripleMatch m)
{
return new TripleMatchIterator(m.asTriple(), db.iterator()) ;
}
}