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Category: CCD-410

Exam CCD-410: Cloudera Certified Developer for Apache Hadoop

Will you be able to reuse your existing Reduces as your combiner in this case and why or why not?

You want to count the number of occurrences for each unique word in the supplied input data.
You’ve decided to implement this by having your mapper tokenize each word and emit a literal
value 1, and then have your reducer increment a counter for each literal 1 it receives. After
successful implementing this, it occurs to you that you could optimize this by specifying a
combiner. Will you be able to reuse your existing Reduces as your combiner in this case and why
or why not?

Determine the difference between setting the number of reduces to one and settings the number of reducers to z

You write MapReduce job to process 100 files in HDFS. Your MapReduce algorithm uses
TextInputFormat: the mapper applies a regular expression over input values and emits key-values
pairs with the key consisting of the matching text, and the value containing the filename and byte
offset. Determine the difference between setting the number of reduces to one and settings the
number of reducers to zero.


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