1 | /** |
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2 | * Licensed to the Apache Software Foundation (ASF) under one |
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3 | * or more contributor license agreements. See the NOTICE file |
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4 | * distributed with this work for additional information |
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5 | * regarding copyright ownership. The ASF licenses this file |
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6 | * to you under the Apache License, Version 2.0 (the |
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7 | * "License"); you may not use this file except in compliance |
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8 | * with the License. You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | |
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19 | package org.apache.hadoop.mapreduce; |
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20 | |
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21 | import java.io.IOException; |
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22 | import java.util.Iterator; |
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23 | import java.util.NoSuchElementException; |
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24 | |
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25 | import org.apache.hadoop.conf.Configuration; |
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26 | import org.apache.hadoop.io.BytesWritable; |
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27 | import org.apache.hadoop.io.DataInputBuffer; |
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28 | import org.apache.hadoop.io.RawComparator; |
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29 | import org.apache.hadoop.io.serializer.Deserializer; |
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30 | import org.apache.hadoop.io.serializer.SerializationFactory; |
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31 | import org.apache.hadoop.mapred.RawKeyValueIterator; |
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32 | import org.apache.hadoop.util.Progressable; |
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33 | |
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34 | /** |
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35 | * The context passed to the {@link Reducer}. |
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36 | * @param <KEYIN> the class of the input keys |
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37 | * @param <VALUEIN> the class of the input values |
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38 | * @param <KEYOUT> the class of the output keys |
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39 | * @param <VALUEOUT> the class of the output values |
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40 | */ |
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41 | public class ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT> |
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42 | extends TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT> { |
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43 | private RawKeyValueIterator input; |
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44 | private Counter inputCounter; |
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45 | private RawComparator<KEYIN> comparator; |
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46 | private KEYIN key; // current key |
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47 | private VALUEIN value; // current value |
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48 | private boolean firstValue = false; // first value in key |
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49 | private boolean nextKeyIsSame = false; // more w/ this key |
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50 | private boolean hasMore; // more in file |
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51 | protected Progressable reporter; |
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52 | private Deserializer<KEYIN> keyDeserializer; |
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53 | private Deserializer<VALUEIN> valueDeserializer; |
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54 | private DataInputBuffer buffer = new DataInputBuffer(); |
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55 | private BytesWritable currentRawKey = new BytesWritable(); |
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56 | private ValueIterable iterable = new ValueIterable(); |
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57 | |
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58 | public ReduceContext(Configuration conf, TaskAttemptID taskid, |
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59 | RawKeyValueIterator input, |
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60 | Counter inputCounter, |
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61 | RecordWriter<KEYOUT,VALUEOUT> output, |
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62 | OutputCommitter committer, |
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63 | StatusReporter reporter, |
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64 | RawComparator<KEYIN> comparator, |
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65 | Class<KEYIN> keyClass, |
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66 | Class<VALUEIN> valueClass |
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67 | ) throws InterruptedException, IOException{ |
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68 | super(conf, taskid, output, committer, reporter); |
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69 | this.input = input; |
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70 | this.inputCounter = inputCounter; |
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71 | this.comparator = comparator; |
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72 | SerializationFactory serializationFactory = new SerializationFactory(conf); |
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73 | this.keyDeserializer = serializationFactory.getDeserializer(keyClass); |
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74 | this.keyDeserializer.open(buffer); |
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75 | this.valueDeserializer = serializationFactory.getDeserializer(valueClass); |
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76 | this.valueDeserializer.open(buffer); |
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77 | hasMore = input.next(); |
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78 | } |
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79 | |
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80 | /** Start processing next unique key. */ |
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81 | public boolean nextKey() throws IOException,InterruptedException { |
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82 | while (hasMore && nextKeyIsSame) { |
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83 | nextKeyValue(); |
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84 | } |
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85 | if (hasMore) { |
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86 | return nextKeyValue(); |
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87 | } else { |
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88 | return false; |
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89 | } |
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90 | } |
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91 | |
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92 | /** |
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93 | * Advance to the next key/value pair. |
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94 | */ |
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95 | @Override |
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96 | public boolean nextKeyValue() throws IOException, InterruptedException { |
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97 | if (!hasMore) { |
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98 | key = null; |
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99 | value = null; |
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100 | return false; |
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101 | } |
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102 | firstValue = !nextKeyIsSame; |
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103 | DataInputBuffer next = input.getKey(); |
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104 | currentRawKey.set(next.getData(), next.getPosition(), |
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105 | next.getLength() - next.getPosition()); |
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106 | buffer.reset(currentRawKey.getBytes(), 0, currentRawKey.getLength()); |
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107 | key = keyDeserializer.deserialize(key); |
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108 | next = input.getValue(); |
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109 | buffer.reset(next.getData(), next.getPosition(), next.getLength()); |
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110 | value = valueDeserializer.deserialize(value); |
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111 | hasMore = input.next(); |
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112 | inputCounter.increment(1); |
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113 | if (hasMore) { |
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114 | next = input.getKey(); |
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115 | nextKeyIsSame = comparator.compare(currentRawKey.getBytes(), 0, |
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116 | currentRawKey.getLength(), |
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117 | next.getData(), |
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118 | next.getPosition(), |
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119 | next.getLength() - next.getPosition() |
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120 | ) == 0; |
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121 | } else { |
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122 | nextKeyIsSame = false; |
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123 | } |
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124 | return true; |
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125 | } |
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126 | |
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127 | public KEYIN getCurrentKey() { |
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128 | return key; |
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129 | } |
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130 | |
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131 | @Override |
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132 | public VALUEIN getCurrentValue() { |
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133 | return value; |
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134 | } |
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135 | |
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136 | protected class ValueIterator implements Iterator<VALUEIN> { |
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137 | |
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138 | @Override |
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139 | public boolean hasNext() { |
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140 | return firstValue || nextKeyIsSame; |
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141 | } |
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142 | |
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143 | @Override |
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144 | public VALUEIN next() { |
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145 | // if this is the first record, we don't need to advance |
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146 | if (firstValue) { |
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147 | firstValue = false; |
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148 | return value; |
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149 | } |
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150 | // if this isn't the first record and the next key is different, they |
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151 | // can't advance it here. |
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152 | if (!nextKeyIsSame) { |
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153 | throw new NoSuchElementException("iterate past last value"); |
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154 | } |
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155 | // otherwise, go to the next key/value pair |
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156 | try { |
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157 | nextKeyValue(); |
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158 | return value; |
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159 | } catch (IOException ie) { |
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160 | throw new RuntimeException("next value iterator failed", ie); |
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161 | } catch (InterruptedException ie) { |
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162 | // this is bad, but we can't modify the exception list of java.util |
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163 | throw new RuntimeException("next value iterator interrupted", ie); |
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164 | } |
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165 | } |
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166 | |
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167 | @Override |
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168 | public void remove() { |
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169 | throw new UnsupportedOperationException("remove not implemented"); |
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170 | } |
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171 | |
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172 | } |
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173 | |
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174 | protected class ValueIterable implements Iterable<VALUEIN> { |
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175 | private ValueIterator iterator = new ValueIterator(); |
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176 | @Override |
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177 | public Iterator<VALUEIN> iterator() { |
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178 | return iterator; |
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179 | } |
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180 | } |
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181 | |
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182 | /** |
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183 | * Iterate through the values for the current key, reusing the same value |
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184 | * object, which is stored in the context. |
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185 | * @return the series of values associated with the current key. All of the |
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186 | * objects returned directly and indirectly from this method are reused. |
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187 | */ |
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188 | public |
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189 | Iterable<VALUEIN> getValues() throws IOException, InterruptedException { |
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190 | return iterable; |
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191 | } |
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192 | } |
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