Databricks Data Engineer Associate Question 294
Single answerA data engineering team is working on optimizing a Delta Lake table used for storing customer transaction data. They have noticed that queries often filter on the 'transaction_date' column. How can Z-Ordering benefit their Delta Lake table in this scenario?
- A
Z-Ordering reduces the size of the Delta Lake table, making it more compact.
- B
Z-Ordering ensures that data is physically sorted by the column being queried, improving the performance of queries with filters.
- C
Z-Ordering automatically partitions the Delta Lake table based on the column being optimized.
- D
Z-Ordering eliminates the need for maintaining Delta Lake table statistics.
Show answer and explanation
Correct answer: B
Explanation
Z-Ordering improves query performance by physically reordering the data in a Delta Lake table based on the specified column. In this scenario, since queries frequently filter on the 'transaction_date' column, applying Z-Ordering on 'transaction_date' will ensure that the relevant data is co-located, reducing the amount of data scanned and speeding up queries.
- A. Incorrect.
Z-Ordering does not directly reduce the size of the Delta Lake table. Instead, it optimizes the data layout for query performance.
- B. Correct.
Z-Ordering physically rearranges data within files in a co-located manner based on the column specified, which improves query performance for filters on that column.
- C. Incorrect.
Z-Ordering is not related to partitioning. Partitioning is a separate optimization strategy in Delta Lake.
- D. Incorrect.
Z-Ordering does not eliminate the need for maintaining table statistics; table statistics still play a role in query planning and optimization.