/**
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 Aug 25, 2010
*/
package com.bigdata.bop.join;
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.BOpUtility;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IConstraint;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.NV;
import com.bigdata.bop.PipelineOp;
import com.bigdata.bop.controller.INamedSolutionSetRef;
import com.bigdata.bop.controller.NamedSetAnnotations;
import com.bigdata.bop.engine.BOpStats;
import com.bigdata.relation.accesspath.IBlockingBuffer;
import com.bigdata.relation.accesspath.UnsyncLocalOutputBuffer;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* This operator performs a nested loop join for solutions. Intermediate
* solutions read from the pipeline are joined against a scan of some other
* solution set. This operator is useful when the cardinality of the source
* solutions in the pipeline is low (typically one empty source solution which
* is exogenous to the query, but it is also cost efficient when there is a
* small set of source solutions to be tested for each solution drained from the
* named solution set). As the number of source solutions to be drained from the
* pipeline grows, it eventually becomes cheaper to build a hash index over the
* named solution set and perform a hash join with the source solutions.
* <p>
* Note: This operator MUST NOT reorder the solutions which are being scanned
* from the named solution set. The query planner relies on that behavior to
* optimize a SLICE from a pre-computed named solution set.
* <p>
*
* @see <a
* href="https://sourceforge.net/apps/mediawiki/bigdata/index.php?title=SPARQL_Update">
* SPARQL Update </a>
*
* @see <a href="https://sourceforge.net/apps/trac/bigdata/ticket/531"> SPARQL
* UPDATE for SOLUTION SETS </a>
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id: CopyOp.java 6010 2012-02-10 20:11:20Z thompsonbry $
*
* TODO This join does not implement optional semantics. If a use case
* for a nested loop join with optional semantics is identified at some
* point, then we will have to add support for optional here (and in
* the test suite).
*/
public class NestedLoopJoinOp extends PipelineOp {
/**
*
*/
private static final long serialVersionUID = 1L;
public interface Annotations extends JoinAnnotations, NamedSetAnnotations {
// /**
// * The name of the pre-existing named solution set to be scanned.
// */
// String NAME = NestedLoopJoinOp.class.getName() + ".name";
}
/**
* Deep copy constructor.
*
* @param op
*/
public NestedLoopJoinOp(final NestedLoopJoinOp op) {
super(op);
}
/**
* Shallow copy constructor.
*
* @param args
* @param annotations
*/
public NestedLoopJoinOp(final BOp[] args,
final Map<String, Object> annotations) {
super(args, annotations);
// MUST be given.
getRequiredProperty(Annotations.NAMED_SET_REF);
}
public NestedLoopJoinOp(final BOp[] args, final NV... annotations) {
this(args, NV.asMap(annotations));
}
// /**
// * @see Annotations#NAME
// */
// protected String getName() {
//
// return (String) getRequiredProperty(Annotations.NAME);
//
// }
/**
* @see Annotations#SELECT
*/
protected IVariable<?>[] getSelect() {
return getProperty(Annotations.SELECT, null/* defaultValue */);
}
/**
* @see Annotations#CONSTRAINTS
*/
protected IConstraint[] constraints() {
return getProperty(Annotations.CONSTRAINTS, null/* defaultValue */);
}
public FutureTask<Void> eval(final BOpContext<IBindingSet> context) {
return new FutureTask<Void>(new ChunkTask(this, context));
}
/**
* Copy the source to the sink.
*/
static private class ChunkTask implements Callable<Void> {
private final NestedLoopJoinOp op;
private final BOpContext<IBindingSet> context;
ChunkTask(final NestedLoopJoinOp op,
final BOpContext<IBindingSet> context) {
this.op = op;
this.context = context;
}
@Override
public Void call() throws Exception {
final BOpStats stats = context.getStats();
// Convert source solutions to array (assumes low cardinality).
final IBindingSet[] leftSolutions = BOpUtility.toArray(
context.getSource(), stats);
// default sink
final IBlockingBuffer<IBindingSet[]> sink = context.getSink();
final UnsyncLocalOutputBuffer<IBindingSet> unsyncBuffer = new UnsyncLocalOutputBuffer<IBindingSet>(
op.getChunkCapacity(), sink);
final IVariable<?>[] selectVars = op.getSelect();
final IConstraint[] constraints = op.constraints();
final ICloseableIterator<IBindingSet[]> ritr = getRightSolutions();
try {
while (ritr.hasNext()) {
final IBindingSet[] a = ritr.next();
for (IBindingSet right : a) {
for (IBindingSet left : leftSolutions) {
// See if the solutions join.
final IBindingSet outSolution = BOpContext.bind(//
right,//
left,//
constraints,//
selectVars//
);
if (outSolution != null) {
// Output the solution.
unsyncBuffer.add(outSolution);
}
}
}
}
// flush the unsync buffer.
unsyncBuffer.flush();
// flush the sink.
sink.flush();
// Done.
return null;
} finally {
sink.close();
context.getSource().close();
if (ritr != null)
ritr.close();
}
}
/**
* Return the right solutions.
*/
protected ICloseableIterator<IBindingSet[]> getRightSolutions() {
final INamedSolutionSetRef namedSetRef = (INamedSolutionSetRef) op
.getRequiredProperty(Annotations.NAMED_SET_REF);
return context.getAlternateSource(namedSetRef);
}
} // class ChunkTask
}