Databricks Certified Data Engineer - Associate

Explanation:

In Databricks Delta Lake, the OPTIMIZE command is specifically designed to compact small files into larger files to improve query performance. Here's why:

1. OPTIMIZE command: This command performs file compaction by merging small files into larger, more efficient files. It's the recommended approach for Delta tables.

2. Why other options are incorrect:

   • REDUCE: Not a valid Delta Lake command for file compaction
   • COMPACTION: While conceptually related, this is not a specific Delta Lake command
   • REPARTITION: This is a Spark transformation that redistributes data across partitions, but it doesn't specifically optimize file sizes in Delta tables
   • VACUUM: This command removes old files that are no longer referenced by the Delta table (data retention cleanup), but doesn't compact existing files

3. How OPTIMIZE works:

   • Merges small Parquet files into larger files
   • Improves read performance by reducing the number of files to scan
   • Can be run on specific partitions using WHERE clause
   • Example usage: OPTIMIZE delta./path/to/table``

4. Best practice: Regular optimization of Delta tables with small files is recommended for maintaining good query performance, especially for tables that receive frequent small writes.