Troubleshooting PostgreSQL Query Performance

Monitoring query latency, wait events, and locks in PostgreSQL helps identify and diagnose performance bottlenecks. Here’s a guide on how to monitor these aspects:

  1. Query Latency:
  • Use the pg_stat_statements extension to track query latencies. You can check the mean_time column in the pg_stat_statements view to find the average query execution time.
  • Configure log_min_duration_statement in postgresql.conf to log queries that take longer than a certain threshold (in milliseconds). Analyze the log to identify slow queries.
  1. Wait Events:
  • Monitor the pg_stat_activity view to check wait events for each backend process. The wait_event_type and wait_event columns indicate the type of wait event and its specific name, respectively.
  • Use tools like pg_activity or PgHero to visualize wait events and identify patterns causing performance issues.
  1. Locks:
  • Examine the pg_locks view to monitor the current lock statuses in the database. Join this view with pg_stat_activity to gather more information about the processes holding or waiting for locks.
  • Monitor the pg_stat_database view to track lock-related metrics such as deadlocks or conflicts. A high number of deadlocks or conflicts could indicate potential lock contention issues.

Here’s a sample query to gather information about locks, wait events, and query latency:

Conclusion

Monitoring query latency, wait events, and locks, and analyzing their trends over time can help you identify and resolve performance bottlenecks in PostgreSQL.

About Shiv Iyer 452 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.