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 java.io.IOException;
021import org.apache.yetus.audience.InterfaceAudience;
022
023/**
024 * Used to separate the row constructing logic.
025 * <p>
026 * After we add heartbeat support for scan, RS may return partial result even if allowPartial is
027 * false and batch is 0. With this interface, the implementation now looks like:
028 * <ol>
029 * <li>Get results from ScanResponse proto.</li>
030 * <li>Pass them to ScanResultCache and get something back.</li>
031 * <li>If we actually get something back, then pass it to ScanConsumer.</li>
032 * </ol>
033 */
034@InterfaceAudience.Private
035interface ScanResultCache {
036
037  static final Result[] EMPTY_RESULT_ARRAY = new Result[0];
038
039  /**
040   * Add the given results to cache and get valid results back.
041   * @param results            the results of a scan next. Must not be null.
042   * @param isHeartbeatMessage indicate whether the results is gotten from a heartbeat response.
043   * @return valid results, never null.
044   */
045  Result[] addAndGet(Result[] results, boolean isHeartbeatMessage) throws IOException;
046
047  /**
048   * Clear the cached result if any. Called when scan error and we will start from a start of a row
049   * again.
050   */
051  void clear();
052
053  /**
054   * Return the number of complete rows. Used to implement limited scan.
055   */
056  int numberOfCompleteRows();
057}