/**
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 Jan 16, 2008
*/
package com.bigdata.btree.proc;
import com.bigdata.service.Split;
/**
* An interface for handling results obtained when an {@link IIndexProcedure} is
* parallelized across either a local index or partitions of a scale-out index.
*
* @param <R>
* The type of the result from applying the procedure to a single
* key-range (or {@link Split}} of data.
* @param <A>
* The type of the aggregated result.
*
* @see BLZG-1537 (Schedule more IOs when loading data)
*
* @todo drop {@link #getResult()} from the signature? The handler
* implementation can expose a custom method when an aggregated return is
* desirable. However some handlers will apply iterative processing to the
* results as they are obtained without any sense of aggregation.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public interface IResultHandler<R extends Object, A extends Object> {
/**
* Method is invoked for each result and is responsible for combining
* the results in whatever manner is meaningful for the procedure.
* Implementations of this method MUST be <strong>thread-safe</strong>
* since the procedure MAY be applied in parallel when it spans more
* than one index partition.
*
* @param result
* The result from applying the procedure to a single index
* partition.
* @param split
* The {@link Split} that generated that result.
*/
public void aggregate(R result, Split split);
/**
* Return the aggregated results as an implementation dependent object.
*/
public A getResult();
}