Databricks Data Engineer Associate Question 293
Select 2You are working with a Delta Lake table containing a large volume of e-commerce transaction data. Queries on the table frequently filter by 'customer_id' and 'transaction_date' columns. How can Z-ordering improve query performance in this scenario?
- A
Z-ordering optimizes data storage layout to co-locate similar column values, reducing file scan time during queries.
- B
Z-ordering compresses the Delta Lake table to reduce its size, leading to faster queries.
- C
Z-ordering improves query performance by reducing the number of partitions in the Delta Lake table.
- D
Z-ordering reorganizes data within files to improve query pruning efficiency for frequently filtered columns.
- E
Z-ordering ensures that Spark automatically caches the table in memory for faster access.
Show answer and explanation
Correct answers: A, D
Explanation
Z-ordering is a data layout optimization technique in Delta Lake that organizes data to co-locate similar values within files. This improves query performance by reducing the amount of data scanned during queries that filter by specific columns. In this scenario, Z-ordering on 'customer_id' and 'transaction_date' would help Spark efficiently prune unnecessary data, resulting in faster queries.
- A. Correct.
This is correct. Z-ordering reorganizes the storage layout of data to cluster similar values together, which minimizes the amount of data scanned during queries involving the specified columns.
- B. Incorrect.
This is incorrect. While Z-ordering changes the physical layout of data, it does not directly compress the table to reduce its size.
- C. Incorrect.
This is incorrect. Z-ordering does not change the number of partitions in the table but reorganizes data within existing partitions.
- D. Correct.
This is correct. Z-ordering arranges data within files in a way that improves query pruning efficiency for columns that are frequently filtered, such as 'customer_id' and 'transaction_date'.
- E. Incorrect.
This is incorrect. Z-ordering is unrelated to caching; it focuses on optimizing the data layout for query performance.