/**
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 Apr 29, 2013
*/
package com.bigdata.bop.join;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.engine.BOpStats;
import com.bigdata.relation.accesspath.IBuffer;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* A "DISTINCT" filter for {@link IBindingSet}s.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public interface IDistinctFilter {
/**
* The variables that are being projected out of the DISTINCT filter. The
* solutions will be DISTINCT on this combination of variables. Bindings on
* other variables will be dropped.
*/
IVariable<?>[] getProjectedVars();
/**
* If the bindings are distinct for the configured variables then return a
* new {@link IBindingSet} consisting of only the selected variables.
*
* @param bset
* The binding set to be filtered.
*
* @return A new {@link IBindingSet} containing only the distinct as bound
* values -or- <code>null</code> if the binding set duplicates a
* solution which was already accepted.
*/
IBindingSet accept(final IBindingSet bset);
/**
* Vectored DISTINCT.
*
* @param itr
* The source solutions.
* @param stats
* Statistics object to be updated.
* @param sink
* The sink onto which the DISTINCT solutions will be written.
* @return The #of DISTINCT solutions.
*/
long filterSolutions(final ICloseableIterator<IBindingSet[]> itr,
final BOpStats stats, final IBuffer<IBindingSet> sink);
/**
* Discard the map backing this filter.
*/
void release();
}