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.Closeable; |
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22 | import java.io.IOException; |
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23 | |
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24 | /** |
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25 | * The record reader breaks the data into key/value pairs for input to the |
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26 | * {@link Mapper}. |
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27 | * @param <KEYIN> |
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28 | * @param <VALUEIN> |
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29 | */ |
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30 | public abstract class RecordReader<KEYIN, VALUEIN> implements Closeable { |
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31 | |
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32 | /** |
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33 | * Called once at initialization. |
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34 | * @param split the split that defines the range of records to read |
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35 | * @param context the information about the task |
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36 | * @throws IOException |
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37 | * @throws InterruptedException |
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38 | */ |
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39 | public abstract void initialize(InputSplit split, |
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40 | TaskAttemptContext context |
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41 | ) throws IOException, InterruptedException; |
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42 | |
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43 | /** |
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44 | * Read the next key, value pair. |
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45 | * @return true if a key/value pair was read |
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46 | * @throws IOException |
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47 | * @throws InterruptedException |
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48 | */ |
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49 | public abstract |
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50 | boolean nextKeyValue() throws IOException, InterruptedException; |
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51 | |
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52 | /** |
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53 | * Get the current key |
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54 | * @return the current key or null if there is no current key |
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55 | * @throws IOException |
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56 | * @throws InterruptedException |
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57 | */ |
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58 | public abstract |
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59 | KEYIN getCurrentKey() throws IOException, InterruptedException; |
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60 | |
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61 | /** |
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62 | * Get the current value. |
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63 | * @return the object that was read |
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64 | * @throws IOException |
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65 | * @throws InterruptedException |
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66 | */ |
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67 | public abstract |
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68 | VALUEIN getCurrentValue() throws IOException, InterruptedException; |
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69 | |
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70 | /** |
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71 | * The current progress of the record reader through its data. |
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72 | * @return a number between 0.0 and 1.0 that is the fraction of the data read |
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73 | * @throws IOException |
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74 | * @throws InterruptedException |
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75 | */ |
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76 | public abstract float getProgress() throws IOException, InterruptedException; |
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77 | |
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78 | /** |
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79 | * Close the record reader. |
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80 | */ |
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81 | public abstract void close() throws IOException; |
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82 | } |
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