/*
* (c) Copyright 2010 Epimorphics Ltd.
* All rights reserved.
* [See end of file]
*/
package tdb.examples;
import org.openjena.atlas.iterator.Filter ;
import org.openjena.atlas.lib.Tuple ;
import com.hp.hpl.jena.graph.Node ;
import com.hp.hpl.jena.query.Dataset ;
import com.hp.hpl.jena.query.Query ;
import com.hp.hpl.jena.query.QueryExecution ;
import com.hp.hpl.jena.query.QueryExecutionFactory ;
import com.hp.hpl.jena.query.QueryFactory ;
import com.hp.hpl.jena.query.ResultSetFormatter ;
import com.hp.hpl.jena.sparql.core.Quad ;
import com.hp.hpl.jena.sparql.sse.SSE ;
import com.hp.hpl.jena.tdb.TDB ;
import com.hp.hpl.jena.tdb.TDBFactory ;
import com.hp.hpl.jena.tdb.nodetable.NodeTable ;
import com.hp.hpl.jena.tdb.store.DatasetGraphTDB ;
import com.hp.hpl.jena.tdb.store.NodeId ;
import com.hp.hpl.jena.tdb.sys.SystemTDB ;
/** Example of how to filter quads as they are accessed at the lowest level.
* Can be used to exclude daat from specific graphs.
* This mechanism is not limited to graphs - it works for properties or anything
* where the visibility of otherwise is determined by the elements of the quad.
* See <a href="http://openjena.org/wiki/TDB/QuadFilter">TDB/QuadFilter</a>
* for further details.
*/
public class ExQuadFilter
{
private static String graphToHide = "http://example/g2" ;
public static void main(String ... args)
{
// This also works for default union graph ....
TDB.getContext().setTrue(TDB.symUnionDefaultGraph) ;
Dataset ds = setup() ;
Filter<Tuple<NodeId>> filter = createFilter(ds) ;
example(ds, filter) ;
}
/** Example setup - in-memory dataset with two graphs, one triple in each */
private static Dataset setup()
{
Dataset ds = TDBFactory.createDataset() ;
DatasetGraphTDB dsg = (DatasetGraphTDB)(ds.asDatasetGraph()) ;
Quad q1 = SSE.parseQuad("(<http://example/g1> <http://example/s> <http://example/p> <http://example/o1>)") ;
Quad q2 = SSE.parseQuad("(<http://example/g2> <http://example/s> <http://example/p> <http://example/o2>)") ;
dsg.add(q1) ;
dsg.add(q2) ;
return ds ;
}
/** Create a filter to exclude the graph http://example/g2 */
private static Filter<Tuple<NodeId>> createFilter(Dataset ds)
{
DatasetGraphTDB dsg = (DatasetGraphTDB)(ds.asDatasetGraph()) ;
final NodeTable nodeTable = dsg.getQuadTable().getNodeTupleTable().getNodeTable() ;
// Filtering operates at a very low level:
// need to know the internal identifier for the graph name.
final NodeId target = nodeTable.getNodeIdForNode(Node.createURI(graphToHide)) ;
System.out.println("Hide graph: "+graphToHide+" --> "+target) ;
// Filter for accept/reject as quad as being visible.
// Return true for "accept", false for "reject"
Filter<Tuple<NodeId>> filter = new Filter<Tuple<NodeId>>() {
public boolean accept(Tuple<NodeId> item)
{
// Reverse the lookup as a demo
//Node n = nodeTable.getNodeForNodeId(target) ;
//System.err.println(item) ;
if ( item.size() == 4 && item.get(0).equals(target) )
{
//System.out.println("Reject: "+item) ;
return false ;
}
//System.out.println("Accept: "+item) ;
return true ;
} } ;
return filter ;
}
private static void example(Dataset ds, Filter<Tuple<NodeId>> filter)
{
String[] x = {
"SELECT * { GRAPH ?g { ?s ?p ?o } }",
"SELECT * { ?s ?p ?o }",
// THis filter does not hide the graph itself, just the quads associated with the graph.
"SELECT * { GRAPH ?g {} }"
} ;
for ( String qs : x )
{
example(ds, qs, filter) ;
example(ds, qs, null) ;
}
}
private static void example(Dataset ds, String qs, Filter<Tuple<NodeId>> filter)
{
System.out.println() ;
Query query = QueryFactory.create(qs) ;
System.out.println(qs) ;
QueryExecution qExec = QueryExecutionFactory.create(query, ds) ;
// Install filter for this query only.
if ( filter != null )
{
System.out.println("Install quad-level filter") ;
qExec.getContext().set(SystemTDB.symTupleFilter, filter) ;
}
else
System.out.println("No quad-level filter") ;
ResultSetFormatter.out(qExec.execSelect()) ;
qExec.close() ;
}
}
/*
* (c) Copyright 2010 Epimorphics Ltd.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/