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courses:mapreduce-tutorial:step-5 [2012/01/29 20:21] straka |
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| As before, Hadoop silently handles failures. It can happen that even a successfully finished mapper needs to be executed again -- if the machine, where its output data were stored, gets disconnected from the network. | As before, Hadoop silently handles failures. It can happen that even a successfully finished mapper needs to be executed again -- if the machine, where its output data were stored, gets disconnected from the network. | ||
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| + | ===== Types of keys and values ===== | ||
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| + | Currently in the Perl API, the keys and values are both strings, which are stored and loaded using UTF-8 format. If you need more complex structures, you have to serialize and deserialize them by yourselves. | ||
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| + | The Java API offers a wide range of types, including user-defined types, to be used for keys and values. | ||
| ===== Exercise 1 ===== | ===== Exercise 1 ===== | ||