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What Is the Role of the Map Function in a Hadoop Word Count Program?
Learn the exact function of the Mapper in Hadoop’s Word Count program. Understand how it tokenizes input text into key-value pairs for your Big Data certification exam preparation.
Question
What does the Map function do in the Word Count program?
A. It processes input text and emits key-value pairs for words
B. It stores final results into HDFS
C. It combines values by key
D. It validates Hadoop cluster performance
Answer
A. It processes input text and emits key-value pairs for words
Explanation
In the Hadoop Word Count program, the Map function serves as the initial processing stage. It takes a block of input text, tokenizes it (usually splitting by spaces to isolate individual words), and emits an intermediate key-value pair for every word it encounters, typically in the format of (word, 1). It does not aggregate these numbers or store the final results into HDFS; instead, it simply passes these intermediate pairs forward to the Reduce phase, where the actual counting and combining of values for each unique key take place.