When a MapReduce application is executed, which of the following actions occurred before the map phase?

Question

Options

• Asplit
• Bcombine
• Cpartition
• Dsort

• A
  77% (20)
• B
  8% (2)
• C
  12% (3)
• D
  4% (1)

Explanation

Split happens before the map phase because MapReduce must divide the input data into fixed-size chunks (input splits) that can each be processed independently by a mapper - without this partitioning of raw input, there would be nothing for mappers to consume. Combine (B) is an optional mini-reducer that runs after mapping to reduce data volume before shuffling - it's a post-map optimization. Partition (C) determines which reducer receives which key-value pairs and occurs during the shuffle phase, between map and reduce. Sort (D) also occurs during the shuffle phase, after partitioning, to order keys before they reach the reducer.

Memory tip: Think of the pipeline order as S-M-C-P-S-R - Split → Map → Combine → Partition → Sort → Reduce. Split is the very first "S," making it the only action that precedes the map phase.

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