/*
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 15, 2008
*/
package com.bigdata.rdf.relation.rule;
import com.bigdata.bop.Constant;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IVariable;
import com.bigdata.btree.keys.IKeyBuilder;
import com.bigdata.btree.keys.ISortKeyBuilder;
import com.bigdata.rdf.internal.IV;
/**
* Builds unsigned byte[] sort keys from {@link IBindingSet}s.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public class BindingSetSortKeyBuilder implements ISortKeyBuilder<IBindingSet> {
private final IKeyBuilder keyBuilder;
private final IVariable[] vars;
/**
*
* @param keyBuilder
* Used to generate the unsigned byte[] key for each bound
* variable. In particular, the configuration for the
* {@link IKeyBuilder} governs how Unicode fields are handled.
* @param vars
* An array of {@link IVariable}s, all of which MUST be bound.
*/
public BindingSetSortKeyBuilder(final IKeyBuilder keyBuilder,
final IVariable[] vars) {
if (keyBuilder == null)
throw new IllegalArgumentException();
if (vars == null || vars.length == 0)
throw new IllegalArgumentException();
this.keyBuilder = keyBuilder;
this.vars = vars;
}
/**
* @todo This has RDF specific handling of the IVs and treatment of unbound
* variables as 0L term identifiers. This needs to be abstracted out
* in order to run against generic relations.
*/
public byte[] getSortKey(final IBindingSet bindingSet) {
keyBuilder.reset();
for (int i = 0; i < vars.length; i++) {
final IVariable<?> var = vars[i];
Object val = bindingSet.get(var);
if (val == null) {
val = Long.valueOf(0);
} else if (val instanceof Constant<?>) {
val = ((Constant<?>) val).get();
}
if (val instanceof IV) {
final IV iv = (IV) val;
iv.encode(keyBuilder);
} else {
keyBuilder.append(val);
}
}
return keyBuilder.getKey();
}
}