phoenix-core/src/main/java/org/apache/phoenix/iterate/MapReduceParallelScanGrouper.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.phoenix.iterate;

import java.util.List;

import org.apache.hadoop.hbase.client.Scan;
import org.apache.phoenix.compile.QueryPlan;

/**
 * Scan grouper that creates a scan group if a plan is row key ordered or if a
 * scan crosses region boundaries
 */
public class MapReduceParallelScanGrouper implements ParallelScanGrouper {
	
	private static final MapReduceParallelScanGrouper INSTANCE = new MapReduceParallelScanGrouper();

    public static MapReduceParallelScanGrouper getInstance() {
        return INSTANCE;
    }
    
    private MapReduceParallelScanGrouper() {}

	@Override
	public boolean shouldStartNewScan(QueryPlan plan, List<Scan> scans,
			byte[] startKey, boolean crossedRegionBoundary) {
		return !plan.isRowKeyOrdered() || crossedRegionBoundary;
	}

}