Google Professional Data Engineer Question 191
Select 3Google Cloud PlatformYou are a Data Engineer managing a BigQuery dataset. A critical query that previously executed in under 10 seconds is now taking over 2 minutes to run. You need to troubleshoot and identify the cause of the poor performance. Which actions should you take?
- A
Check the query execution plan using the BigQuery Query Plan feature.
- B
Review recent changes to the dataset schema or table partitions.
- C
Increase the number of slots assigned to your BigQuery project.
- D
Confirm whether data skew is causing uneven distribution of the workload.
- E
Upgrade the dataset storage from regional to multi-regional.
Show answer and explanation
Correct answers: A, B, D
Explanation
Troubleshooting poor performing queries requires analyzing query execution plans, understanding recent changes to the schema or partitioning, and identifying factors like data skew that impact performance. Increasing slots or upgrading storage are not relevant solutions to pinpoint the cause of slow queries in this scenario.
- A. Correct.
Checking the query execution plan using the BigQuery Query Plan feature helps identify inefficiencies such as cross-joins, missing indexes, or suboptimal table scans.
- B. Correct.
Recent changes to the dataset schema or table partitions can significantly affect query performance, especially if partitioning or clustering has been altered.
- C. Incorrect.
Increasing the number of slots does not address the root cause of poor query performance and is not an effective troubleshooting step for this scenario.
- D. Correct.
Data skew can cause uneven distribution of workloads, leading to some workers taking significantly longer to process data. Identifying and addressing skew is a critical step for resolving performance issues.
- E. Incorrect.
Upgrading the dataset storage from regional to multi-regional will not directly impact query performance and is unrelated to the issue described.