/**
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 Oct 29, 2011
*/
package com.bigdata.bop.solutions;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import com.bigdata.bop.BOp;
import com.bigdata.bop.BOpContext;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.NV;
import com.bigdata.bop.PipelineOp;
import com.bigdata.bop.engine.BOpStats;
import com.bigdata.bop.join.JoinAnnotations;
import com.bigdata.relation.accesspath.IBlockingBuffer;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Operator projects only the identified variables.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public class ProjectionOp extends PipelineOp {
/**
*
*/
private static final long serialVersionUID = 1L;
public interface Annotations extends PipelineOp.Annotations {
/**
* An {@link IVariable}[] identifying the variables to be retained in
* the {@link IBindingSet}s written out by the operator.
*/
String SELECT = JoinAnnotations.SELECT;
}
/**
* @param op
*/
public ProjectionOp(final ProjectionOp op) {
super(op);
}
/**
* @param args
* @param annotations
*/
public ProjectionOp(final BOp[] args, final Map<String, Object> annotations) {
super(args, annotations);
}
public ProjectionOp(final BOp[] args, final NV... annotations) {
this(args, NV.asMap(annotations));
}
/**
* @see Annotations#SELECT
*/
public IVariable<?>[] getVariables() {
return (IVariable<?>[]) getRequiredProperty(Annotations.SELECT);
}
@Override
public FutureTask<Void> eval(final BOpContext<IBindingSet> context) {
return new FutureTask<Void>(new ChunkTask(this, context));
}
/**
* Task executing on the node.
*/
static private class ChunkTask implements Callable<Void> {
private final BOpContext<IBindingSet> context;
/**
* The projected variables.
*/
private final IVariable<?>[] vars;
ChunkTask(final ProjectionOp op, final BOpContext<IBindingSet> context) {
this.context = context;
this.vars = op.getVariables();
if (vars == null)
throw new IllegalArgumentException();
// @see #946 (Empty PROJECTION causes IllegalArgumentException)
// if (vars.length == 0)
// throw new IllegalArgumentException();
}
@Override
public Void call() throws Exception {
final BOpStats stats = context.getStats();
final ICloseableIterator<IBindingSet[]> itr = context
.getSource();
final IBlockingBuffer<IBindingSet[]> sink = context.getSink();
try {
while (itr.hasNext()) {
final IBindingSet[] a = itr.next();
stats.chunksIn.increment();
stats.unitsIn.add(a.length);
for (int i = 0; i < a.length; i++) {
a[i] = a[i].copy(vars);
}
sink.add(a);
}
sink.flush();
// done.
return null;
} finally {
sink.close();
}
}
}
}