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.filterCells;
021
022import java.io.IOException;
023import java.util.Arrays;
024import org.apache.hadoop.hbase.CellUtil;
025import org.apache.hadoop.hbase.ExtendedCell;
026import org.apache.yetus.audience.InterfaceAudience;
027
028/**
029 * A ScanResultCache that may return partial result.
030 * <p>
031 * As we can only scan from the starting of a row when error, so here we also implement the logic
032 * that skips the cells that have already been returned.
033 */
034@InterfaceAudience.Private
035class AllowPartialScanResultCache implements ScanResultCache {
036
037  // used to filter out the cells that already returned to user as we always start from the
038  // beginning of a row when retry.
039  private ExtendedCell lastCell;
040
041  private boolean lastResultPartial;
042
043  private int numberOfCompleteRows;
044
045  private void recordLastResult(Result result) {
046    lastCell = result.rawExtendedCells()[result.rawExtendedCells().length - 1];
047    lastResultPartial = result.mayHaveMoreCellsInRow();
048  }
049
050  @Override
051  public Result[] addAndGet(Result[] results, boolean isHeartbeatMessage) throws IOException {
052    if (results.length == 0) {
053      if (!isHeartbeatMessage && lastResultPartial) {
054        // An empty non heartbeat result indicate that there must be a row change. So if the
055        // lastResultPartial is true then we need to increase numberOfCompleteRows.
056        numberOfCompleteRows++;
057      }
058      return EMPTY_RESULT_ARRAY;
059    }
060    int i;
061    for (i = 0; i < results.length; i++) {
062      Result r = filterCells(results[i], lastCell);
063      if (r != null) {
064        results[i] = r;
065        break;
066      }
067    }
068    if (i == results.length) {
069      return EMPTY_RESULT_ARRAY;
070    }
071    if (lastResultPartial && !CellUtil.matchingRows(lastCell, results[0].getRow())) {
072      // there is a row change, so increase numberOfCompleteRows
073      numberOfCompleteRows++;
074    }
075    recordLastResult(results[results.length - 1]);
076    if (i > 0) {
077      results = Arrays.copyOfRange(results, i, results.length);
078    }
079    for (Result result : results) {
080      if (!result.mayHaveMoreCellsInRow()) {
081        numberOfCompleteRows++;
082      }
083    }
084    return results;
085  }
086
087  @Override
088  public void clear() {
089    // we do not cache anything
090  }
091
092  @Override
093  public int numberOfCompleteRows() {
094    return numberOfCompleteRows;
095  }
096}