Databricks Certified Data Engineer - Associate

Explanation

The correct answer is OPTIMIZE.

Why OPTIMIZE is correct:

• In Delta Lake, the OPTIMIZE command is specifically designed to compact small files into larger files to improve query performance.
• OPTIMIZE reorganizes the data layout by merging small files into larger ones, which reduces the number of files that need to be read during queries.
• This is a common operation in Delta Lake to address the "small file problem" that can occur with frequent small writes.

Why other options are incorrect:

• VACUUM: This command is used to remove old files that are no longer referenced by the Delta table (files older than the retention period). It's for cleaning up storage, not for compacting files.
• COMPACTIO N: This appears to be a typo or misspelling of "COMPACTION" and is not a valid Delta Lake command.
• REPARTITION: While REPARTITION can affect file sizes by changing the number of partitions, it's not specifically designed for compacting existing small files. REPARTITION is typically used during data writing or transformation, not for optimizing existing tables.

Key takeaway: When you need to compact small files in a Delta table to improve read performance, use the OPTIMIZE command. This is a best practice for maintaining efficient data layouts in Delta Lake.