[120] | 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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