001/**
002 * Copyright The Apache Software Foundation
003 *
004 * Licensed to the Apache Software Foundation (ASF) under one or more
005 * contributor license agreements. See the NOTICE file distributed with this
006 * work for additional information regarding copyright ownership. The ASF
007 * licenses this file to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 *
011 * http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
015 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
016 * License for the specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.hadoop.hbase.regionserver;
020
021import java.io.IOException;
022import java.util.List;
023
024import org.apache.hadoop.hbase.Cell;
025import org.apache.hadoop.hbase.DoNotRetryIOException;
026import org.apache.hadoop.hbase.HConstants;
027import org.apache.hadoop.hbase.PrivateCellUtil;
028import org.apache.hadoop.hbase.client.Scan;
029import org.apache.hadoop.hbase.regionserver.HRegion.RegionScannerImpl;
030import org.apache.hadoop.hbase.util.Bytes;
031import org.apache.yetus.audience.InterfaceAudience;
032
033/**
034 * ReversibleRegionScannerImpl extends from RegionScannerImpl, and is used to
035 * support reversed scanning.
036 */
037@InterfaceAudience.Private
038class ReversedRegionScannerImpl extends RegionScannerImpl {
039
040  /**
041   * @param scan
042   * @param additionalScanners
043   * @param region
044   * @throws IOException
045   */
046  ReversedRegionScannerImpl(Scan scan, List<KeyValueScanner> additionalScanners, HRegion region)
047      throws IOException {
048    region.super(scan, additionalScanners, region);
049  }
050
051  @Override
052  protected void initializeKVHeap(List<KeyValueScanner> scanners,
053      List<KeyValueScanner> joinedScanners, HRegion region) throws IOException {
054    this.storeHeap = new ReversedKeyValueHeap(scanners, comparator);
055    if (!joinedScanners.isEmpty()) {
056      throw new DoNotRetryIOException("Reverse scan with loading CFs on demand is not supported");
057    }
058  }
059
060  @Override
061  protected boolean shouldStop(Cell currentRowCell) {
062    if (currentRowCell == null) {
063      return true;
064    }
065    if (stopRow == null || Bytes.equals(stopRow, HConstants.EMPTY_START_ROW)) {
066      return false;
067    }
068    int c = comparator.compareRows(currentRowCell, stopRow, 0, stopRow.length);
069    return c < 0 || (c == 0 && !includeStopRow);
070  }
071
072  @Override
073  protected boolean nextRow(ScannerContext scannerContext, Cell curRowCell)
074      throws IOException {
075    assert super.joinedContinuationRow == null : "Trying to go to next row during joinedHeap read.";
076    this.storeHeap.seekToPreviousRow(PrivateCellUtil.createFirstOnRow(curRowCell));
077    resetFilters();
078    // Calling the hook in CP which allows it to do a fast forward
079    if (this.region.getCoprocessorHost() != null) {
080      return this.region.getCoprocessorHost().postScannerFilterRow(this, curRowCell);
081    }
082    return true;
083  }
084
085}