hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NoLimitScannerContext.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.regionserver;
  19
  20 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  21 import org.apache.yetus.audience.InterfaceAudience;
  22 import org.apache.yetus.audience.InterfaceStability;
  23
  24 /**
  25  * This is a special {@link ScannerContext} subclass that is designed to be used globally when
  26  * limits should not be enforced during invocations of {@link InternalScanner#next(java.util.List)}
  27  * or {@link RegionScanner#next(java.util.List)}.
  28  * <p>
  29  * Instances of {@link NoLimitScannerContext} are immutable after construction. Any attempt to
  30  * change the limits or progress of a {@link NoLimitScannerContext} will fail silently. The net
  31  * effect is that all limit checks will return false, thus indicating that a limit has not been
  32  * reached.
  33  */
  34 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
  35 @InterfaceStability.Evolving
  36 public class NoLimitScannerContext extends ScannerContext {
  37
  38   public NoLimitScannerContext() {
  39     super(false, null, false);
  40   }
  41
  42   /**
  43    * Use this instance whenever limits do not need to be enforced.
  44    */
  45   private static final ScannerContext NO_LIMIT = new NoLimitScannerContext();
  46
  47   /**
  48    * @return The static, immutable instance of {@link NoLimitScannerContext} to be used whenever
  49    *         limits should not be enforced
  50    */
  51   public static final ScannerContext getInstance() {
  52     return NO_LIMIT;
  53   }
  54
  55   @Override
  56   void setKeepProgress(boolean keepProgress) {
  57     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  58   }
  59
  60   @Override
  61   void setBatchProgress(int batchProgress) {
  62     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  63   }
  64
  65   @Override
  66   void setSizeProgress(long sizeProgress, long heapSizeProgress) {
  67     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  68   }
  69
  70   @Override
  71   void setProgress(int batchProgress, long sizeProgress, long heapSizeProgress) {
  72     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  73   }
  74
  75   @Override
  76   void clearProgress() {
  77     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  78   }
  79
  80   @Override
  81   void setSizeLimitScope(LimitScope scope) {
  82     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  83   }
  84
  85   @Override
  86   void setTimeLimitScope(LimitScope scope) {
  87     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  88   }
  89
  90   @Override
  91   NextState setScannerState(NextState state) {
  92     // Do nothing. NoLimitScannerContext instances are immutable post-construction
  93     return state;
  94   }
  95
  96   @Override
  97   boolean checkBatchLimit(LimitScope checkerScope) {
  98     // No limits can be specified, thus return false to indicate no limit has been reached.
  99     return false;
 100   }
 101
 102   @Override
 103   boolean checkSizeLimit(LimitScope checkerScope) {
 104     // No limits can be specified, thus return false to indicate no limit has been reached.
 105     return false;
 106   }
 107
 108   @Override
 109   boolean checkTimeLimit(LimitScope checkerScope) {
 110     // No limits can be specified, thus return false to indicate no limit has been reached.
 111     return false;
 112   }
 113
 114   @Override
 115   boolean checkAnyLimitReached(LimitScope checkerScope) {
 116     return false;
 117   }
 118 }