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Exam Certified Associate Developer for Apache Spark All Questions

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Exam Certified Associate Developer for Apache Spark topic 1 question 47 discussion

Actual exam question from Databricks's Certified Associate Developer for Apache Spark
Question #: 47
Topic #: 1
[All Certified Associate Developer for Apache Spark Questions]

The code block shown below contains an error. The code block is intended to return a new 12-partition DataFrame from the 8-partition DataFrame storesDF by inducing a shuffle. Identify the error.
Code block:
storesDF.coalesce(12)

  • A. The coalesce() operation cannot guarantee the number of target partitions – the repartition() operation should be used instead.
  • B. The coalesce() operation does not induce a shuffle and cannot increase the number of partitions – the repartition() operation should be used instead.
  • C. The coalesce() operation will only work if the DataFrame has been cached to memory – the repartition() operation should be used instead.
  • D. The coalesce() operation requires a column by which to partition rather than a number of partitions – the repartition() operation should be used instead.
  • E. The number of resulting partitions, 12, is not achievable for an 8-partition DataFrame.
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Suggested Answer: B 🗳️
by 4be8126 at May 3, 2023, 10:56 a.m.

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Raju_Bhai
1 year, 1 month ago
with version 3.4.0, df.repartition(12).coalesce(16).rdd.getNumPartitions() returns 12. it doesn't throw error, but only doesn't increase partition either
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4be8126
1 year, 6 months ago
Selected Answer: B
The correct answer is B. The coalesce() operation can decrease the number of partitions but cannot increase the number of partitions. It also does not induce a shuffle, and is therefore more efficient when decreasing the number of partitions. If the goal is to increase the number of partitions, repartition() should be used instead.
upvoted 3 times
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