hbase-client/src/main/java/org/apache/hadoop/hbase/client/ScanResultCache.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.client;
  19
  20 import java.io.IOException;
  21
  22 import org.apache.yetus.audience.InterfaceAudience;
  23
  24 /**
  25  * Used to separate the row constructing logic.
  26  * <p>
  27  * After we add heartbeat support for scan, RS may return partial result even if allowPartial is
  28  * false and batch is 0. With this interface, the implementation now looks like:
  29  * <ol>
  30  * <li>Get results from ScanResponse proto.</li>
  31  * <li>Pass them to ScanResultCache and get something back.</li>
  32  * <li>If we actually get something back, then pass it to ScanConsumer.</li>
  33  * </ol>
  34  */
  35 @InterfaceAudience.Private
  36 interface ScanResultCache {
  37
  38   static final Result[] EMPTY_RESULT_ARRAY = new Result[0];
  39
  40   /**
  41    * Add the given results to cache and get valid results back.
  42    * @param results the results of a scan next. Must not be null.
  43    * @param isHeartbeatMessage indicate whether the results is gotten from a heartbeat response.
  44    * @return valid results, never null.
  45    */
  46   Result[] addAndGet(Result[] results, boolean isHeartbeatMessage) throws IOException;
  47
  48   /**
  49    * Clear the cached result if any. Called when scan error and we will start from a start of a row
  50    * again.
  51    */
  52   void clear();
  53
  54   /**
  55    * Return the number of complete rows. Used to implement limited scan.
  56    */
  57   int numberOfCompleteRows();
  58 }