Databricks Data Engineer Professional Question 32
Select 3A data engineer is designing a Delta table to be used with Databricks SQL for reporting and ad-hoc analytics. The table is expected to handle high query concurrency and must provide optimal performance for SELECT queries. Which actions should the engineer take to optimize the Delta table for Databricks SQL?
- A
Partition the Delta table using columns with high cardinality, such as unique IDs.
- B
Use Z-Ordering on the Delta table to optimize data skipping for frequent query filter columns.
- C
Enable Delta caching to improve query performance for frequently accessed data.
- D
Configure the Delta table to automatically optimize file sizes by enabling Auto Optimize.
- E
Use OPTIMIZE with a ZORDER BY clause after loading data to reorganize files for faster queries.
Show answer and explanation
Correct answers: B, D, E
Explanation
To optimize Delta tables for Databricks SQL, engineers should focus on techniques that enhance query performance, such as Z-Ordering for data skipping, enabling Auto Optimize for efficient file management, and running OPTIMIZE with ZORDER BY to reorganize files. Partitioning should be used cautiously and only on appropriate columns, while Delta caching is less relevant to Databricks SQL service optimizations.
- A. Incorrect.
Partitioning on columns with high cardinality (e.g., unique IDs) can lead to too many small files and degrade query performance, especially in Databricks SQL. Partitioning should be applied to low- to medium-cardinality columns.
- B. Correct.
Z-Ordering reorders data files to optimize data skipping for queries filtering on specific columns, which significantly improves performance in Databricks SQL.
- C. Incorrect.
Delta caching is useful for iterative workloads in Spark but does not directly influence the performance of Databricks SQL queries.
- D. Correct.
Enabling Auto Optimize ensures that Delta table writes automatically optimize file sizes, which helps maintain efficient table structures for Databricks SQL workloads.
- E. Correct.
Using OPTIMIZE alongside ZORDER BY rearranges the data layout and consolidates small files, which improves query performance in Databricks SQL.