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Question 1
Question
You have a large dataset of key value pairs, where the keys are strings and the values are the integers. For each unique key, you want to identify the largest integer. In writing a MapReduce program to accomplish this, can you take advantage of a combiner?
Answer
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No, a combiner would not be useful in this case.
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Yes.
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Yes, but the number of unique keys must be known in advance.
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Yes, as long as all the keys fit into memory on each node.
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Yes, as long as all the integer values that share the same key fit into memory on each node.
Question 2
Question
Given the following code from a MapReduce application:
Job job = new Job(getConf(), "MyMapReduceJob");
Path in = new Path(“source1”, “source2”);
Path out = new Path(“dest1”);
FileInputFormat.setInputPaths(job, in);
FileOutputFormat.setOutputPath(job, out);
Which one of the following statements is true?
Answer
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The input for this job will be the contents of the source1/source2 folder
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The input for this job will be the contents of both the source1 and source2 files
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The input of this job cannot be determined by the code above
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The output of this job will be the source1/source2 folder
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