001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.client;
019
020import static org.apache.hadoop.hbase.client.ConnectionUtils.noMoreResultsForReverseScan;
021
022import java.io.IOException;
023import java.util.concurrent.ExecutorService;
024import org.apache.hadoop.conf.Configuration;
025import org.apache.hadoop.hbase.TableName;
026import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
027import org.apache.yetus.audience.InterfaceAudience;
028
029/**
030 * A reversed client scanner which support backward scanning
031 */
032@InterfaceAudience.Private
033public class ReversedClientScanner extends ClientScanner {
034
035  /**
036   * Create a new ReversibleClientScanner for the specified table Note that the passed
037   * {@link Scan}'s start row maybe changed.
038   */
039  public ReversedClientScanner(Configuration conf, Scan scan, TableName tableName,
040    ClusterConnection connection, RpcRetryingCallerFactory rpcFactory,
041    RpcControllerFactory controllerFactory, ExecutorService pool, int scanReadRpcTimeout,
042    int scannerTimeout, int primaryOperationTimeout) throws IOException {
043    super(conf, scan, tableName, connection, rpcFactory, controllerFactory, pool,
044      scanReadRpcTimeout, scannerTimeout, primaryOperationTimeout);
045  }
046
047  @Override
048  protected boolean setNewStartKey() {
049    if (noMoreResultsForReverseScan(scan, currentRegion)) {
050      return false;
051    }
052    scan.withStartRow(currentRegion.getStartKey(), false);
053    return true;
054  }
055
056  @Override
057  protected ReversedScannerCallable createScannerCallable() {
058    return new ReversedScannerCallable(getConnection(), getTable(), scan, this.scanMetrics,
059      this.rpcControllerFactory, getScanReplicaId());
060  }
061}