Troubleshooting memory intensive queries in PostgreSQL - shiviyer/Blogs GitHub Wiki

Troubleshooting memory-intensive queries in PostgreSQL involves identifying queries that are using excessive memory and optimizing them. Here’s how you can do it:

1. Identify Problematic Queries:

  • Use the pg_stat_statements extension to identify queries with high memory usage.
  • Look for queries with high execution times or those frequently executed.

2. Analyze Query Plans:

  • Use EXPLAIN and EXPLAIN ANALYZE to understand the query plan and see where most memory is being consumed.

3. Adjust work_mem:

  • If a query is using more memory than allocated by work_mem, consider increasing it.
  • Be cautious, as this setting is per operation. Large settings can lead to excessive overall memory consumption, especially with multiple concurrent queries.

4. Optimize Queries:

  • Rewrite inefficient queries. Break down complex queries into simpler ones.
  • Use indexes effectively to reduce the need for large sorts or hash operations.

5. Optimize Data Model:

  • Normalize data where appropriate.
  • Partition large tables to make queries more efficient.
  1. Server Configuration:
    • Ensure the server's overall memory settings are optimized (shared_buffers, effective_cache_size).

7. Monitor Performance:

  • Continuously monitor the server's performance after making changes.
  • Use tools like pgBadger for detailed analysis.

8. Hardware Considerations:

  • If memory issues persist, consider scaling up the server’s hardware, especially RAM.

9. Regular Maintenance:

  • Run VACUUM, ANALYZE, and REINDEX regularly to maintain database performance.

By systematically analyzing and optimizing the queries and server configuration, you can mitigate issues related to memory-intensive queries in PostgreSQL.

Source: https://minervadb.xyz/the-possible-reason-why-you-see-lwlocktranche-buffer_mapping-wait-event-in-postgresql/