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Exam Certified Data Engineer Professional topic 1 question 121 discussion

Actual exam question from Databricks's Certified Data Engineer Professional
Question #: 121
Topic #: 1
[All Certified Data Engineer Professional Questions]

A Databricks SQL dashboard has been configured to monitor the total number of records present in a collection of Delta Lake tables using the following query pattern:


SELECT COUNT (*) FROM table -

Which of the following describes how results are generated each time the dashboard is updated?

  • A. The total count of rows is calculated by scanning all data files
  • B. The total count of rows will be returned from cached results unless REFRESH is run
  • C. The total count of records is calculated from the Delta transaction logs
  • D. The total count of records is calculated from the parquet file metadata
Show Suggested Answer Hide Answer
Suggested Answer: C 🗳️
by MDWPartners at May 30, 2024, 9:13 a.m.

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AlejandroU
1 month, 1 week ago
Answer is D. This is same question #63. Delta Lake stores its data in Parquet format. Parquet files include metadata (like row counts) that can be efficiently queried. For a COUNT(*) query, Delta Lake does not need to scan all the data files; instead, it reads the row count information stored in the Parquet file metadata, making the operation faster.
upvoted 1 times
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vexor3
6 months, 3 weeks ago
Selected Answer: C
C is correct
upvoted 1 times
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hpkr
7 months, 3 weeks ago
Selected Answer: C
C is correct
upvoted 1 times
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BrianNguyen95
8 months ago
Selected Answer: C
Delta Lake optimizes COUNT(*) queries by reading the row counts stored in the Delta transaction log. This eliminates the need for a full table scan, resulting in significantly faster query performance. pen_spark
upvoted 1 times
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Freyr
8 months, 1 week ago
Selected Answer: C
Correct Answer: C
upvoted 1 times
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MDWPartners
8 months, 1 week ago
Selected Answer: C
I would've said C
upvoted 2 times
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