What is the preferred method for analyzing the execution time of queries in BigQuery?

For analyzing the execution time of queries in BigQuery, leveraging Stackdriver Monitoring is the appropriate approach. Stackdriver Monitoring provides comprehensive visibility into the performance of your Google Cloud services, including BigQuery. It allows you to monitor various metrics, such as query execution times, slot usage, and more. By accessing the monitoring interface, you can view detailed time-series graphs and set up alerts for specific thresholds, enabling you to track the performance of your queries over time effectively.

In this context, Stackdriver Monitoring is designed to give a holistic view of service performance and resource utilization, which is essential for optimizing query performance and troubleshooting issues related to execution time.

Other methods mentioned, while useful for different aspects of performance analysis, do not directly focus on query execution times in BigQuery. For instance, Stackdriver Trace is more geared towards tracing application performance and API call execution times rather than examining the specific execution duration of SQL queries in BigQuery. Thus, the most effective and specialized tool for analyzing query execution time is indeed Stackdriver Monitoring.