Databricks Certified Data Engineer - Associate
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A data engineer has realized that the data files associated with a Delta table are incredibly small. They want to compact the small files to form larger files to improve performance.
Which keyword can be used to compact the small files?
Real Exam
Community
KKeng
A
OPTIMIZE
B
VACUUM
C
COMPACTION
D
REPARTITION
Explanation:
Explanation
The correct answer is A. OPTIMIZE.
Why OPTIMIZE is correct:
- In Delta Lake, the
OPTIMIZEcommand is specifically designed to compact small files into larger files to improve read performance. OPTIMIZEreorganizes the data layout by merging small files into larger, more efficient files while maintaining data consistency.- This process is often referred to as "compaction" or "bin-packing" in Delta Lake terminology.
Why other options are incorrect:
- B. VACUUM: This command is used to remove old data files that are no longer referenced by the Delta table (data files older than the retention period). It does not compact small files.
- C. COMPACTION: While this describes the process, it is not an actual SQL command keyword in Delta Lake. The actual command is
OPTIMIZE. - D. REPARTITION: This is a Spark transformation that redistributes data across partitions, but it's not a Delta Lake-specific command for file compaction. While it can affect file sizes,
OPTIMIZEis the dedicated command for this purpose in Delta Lake.
Example usage:
OPTIMIZE table_name
OPTIMIZE table_name
Additional notes:
OPTIMIZEcan be run on the entire table or on specific partitions.- It uses a bin-packing algorithm to combine small files while respecting the target file size.
- This improves query performance by reducing the number of files that need to be read.
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