/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Sep 20, 2010
*/
package com.bigdata.bop.rdf.join;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import com.bigdata.bop.BOp;
import com.bigdata.bop.BOpContext;
import com.bigdata.bop.BOpEvaluationContext;
import com.bigdata.bop.Constant;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IConstant;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.NV;
import com.bigdata.bop.PipelineOp;
import com.bigdata.bop.engine.BOpStats;
import com.bigdata.rdf.internal.IV;
import com.bigdata.relation.accesspath.IBlockingBuffer;
import com.bigdata.relation.accesspath.UnsynchronizedArrayBuffer;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* DataSetJoin(left)[var=g; graphs={graphIds}]
* <p>
* SPARQL specific join of the source binding sets with an inline access path
* allowing <i>var</i> to take on the given graphIds values. This join operator
* is useful when the multiplicity of the graphs is small to moderate. If there
* are a very large number of graphs, then the operator tree is to cumbersome
* and you would do better off joining against an index (whether temporary or
* permanent) containing the graphs.
* <p>
* The evaluation context is {@link BOpEvaluationContext#ANY}.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public class DataSetJoin extends PipelineOp {
/**
*
*/
private static final long serialVersionUID = 1L;
public interface Annotations extends PipelineOp.Annotations {
/**
* The variable to be bound.
*/
String VAR = DataSetJoin.class.getName() + ".var";
/**
* The {@link Set} of {@link IV}s to be bound. A {@link LinkedHashSet}
* should be used for efficiency since it provides fast ordered scans
* and fast point tests.
*/
String GRAPHS = DataSetJoin.class.getName() + ".graphs";
}
/**
* Deep copy constructor.
*
* @param op
*/
public DataSetJoin(final DataSetJoin op) {
super(op);
}
/**
* Shallow copy constructor.
* @param args
* @param annotations
*/
public DataSetJoin(final BOp[] args, final Map<String, Object> annotations) {
super(args, annotations);
getVar();
getGraphs();
}
public DataSetJoin(final BOp[] args, final NV... annotations) {
this(args, NV.asMap(annotations));
}
public IVariable<?> getVar() {
return (IVariable<?>) getRequiredProperty(Annotations.VAR);
}
@SuppressWarnings({ "unchecked", "rawtypes" })
public Set<IV> getGraphs() {
return (Set<IV>) getRequiredProperty(Annotations.GRAPHS);
}
@Override
public FutureTask<Void> eval(final BOpContext<IBindingSet> context) {
return new FutureTask<Void>(new DataSetJoinTask(this,context));
}
/**
* Specialized in-memory join.
*/
static private class DataSetJoinTask implements Callable<Void> {
private final DataSetJoin op;
private final BOpContext<IBindingSet> context;
private final IVariable<?> var;
@SuppressWarnings("rawtypes")
private final Set<IV> graphs;
DataSetJoinTask(final DataSetJoin op,
final BOpContext<IBindingSet> context) {
this.op = op;
this.context = context;
var = op.getVar();
graphs = op.getGraphs();
}
@Override
public Void call() throws Exception {
final ICloseableIterator<IBindingSet[]> source = context
.getSource();
final IBlockingBuffer<IBindingSet[]> sink = context.getSink();
try {
final BOpStats stats = context.getStats();
final UnsynchronizedArrayBuffer<IBindingSet> tmp = new UnsynchronizedArrayBuffer<IBindingSet>(
sink, IBindingSet.class, op.getChunkCapacity());
while (source.hasNext()) {
final IBindingSet[] chunk = source.next();
stats.chunksIn.increment();
stats.unitsIn.add(chunk.length);
handleChunk(chunk, tmp);
}
tmp.flush();
sink.flush();
return null;
} finally {
sink.close();
source.close();
}
}
/**
* Join source binding set chunk with {@link #graphs}.
*
* @param chunk
* A chunk of {@link IBindingSet}s from the source.
* @param tmp
* Where to write the data.
*/
@SuppressWarnings("rawtypes")
private void handleChunk(final IBindingSet[] chunk,
final UnsynchronizedArrayBuffer<IBindingSet> tmp) {
for (IBindingSet bset : chunk) {
final IConstant val = bset.get(var);
if (val == null) {
/*
* When the value is unbound, we output the cross product.
*/
for (IV c : graphs) {
bset = bset.clone();
bset.set(var, new Constant<IV>(c));
tmp.add(bset);
}
} else {
/*
* When the value is bound the binding set will be output
* iff the bound value for the variable is found in the
* specified graphs.
*/
if (graphs.contains(val.get())) {
// match. output binding set.
tmp.add(bset);
}
}
}
}
}
}