Concurrent statistics gathering in PostgreSQL allows the system to collect table and column statistics without blocking concurrent read and write operations. As a result, this feature ensures accurate and up-to-date statistics while minimizing the impact on overall database performance. Here’s how you can implement concurrent statistics gathering in PostgreSQL:
-
Enable Autovacuum:
Concurrent statistics gathering relies on the autovacuum process to collect statistics automatically. Make sure autovacuum is enabled in your PostgreSQL configuration file (postgresql.conf). Set the autovacuum parameter to on to enable the autovacuum process.
-
Configure Statistics Target:
Next, determine the desired level of detail for statistics. You can do this by setting the default_statistics_target parameter in the PostgreSQL configuration file. This parameter controls the number of sampled rows used to estimate statistics. While higher values provide more accurate statistics, they also require more processing time.
-
Enable Autoanalyze:
Then, ensure that autoanalyze—an essential sub-process of autovacuum responsible for collecting statistics—is enabled. Although PostgreSQL enables it by default, it’s important to verify its status in the postgresql.conf file. Set the autoanalyze parameter to on to confirm it’s active.
-
Tune Autovacuum Settings:
After enabling the processes, adjust the autovacuum-related parameters to suit your workload and performance requirements. Key parameters include autovacuum_vacuum_scale_factor, autovacuum_analyze_scale_factor, and autovacuum_vacuum_threshold. These settings determine when PostgreSQL triggers autovacuum processes based on table size and activity level.
-
Monitor and Adjust:
Monitor the autovacuum and autoanalyze processes using system catalogs such as pg_stat_all_tables and pg_stat_progress_vacuum. Observe their behavior, including the frequency of statistics collection and the impact on system resources. If necessary, adjust the autovacuum-related parameters to fine-tune the process for your workload.
By implementing concurrent statistics gathering in PostgreSQL, you can ensure that statistics remain up-to-date without interfering with concurrent read and write operations. This helps the query optimizer make informed decisions and improves overall query performance. Regularly monitoring and adjusting autovacuum settings can further optimize the statistics collection process based on the specific needs of your database.
