Auto-explain is an extension that helps the database administrator get an idea of slow queries and their execution plan. Essentially, auto-explain triggers when a running query is slower than a specified threshold, and then dumps in the PostgreSQL logs (refer to Chapter 14, Logging and Auditing) the execution plan of the query.
In this way, the database administrator can get an insight into slow queries and their execution plan without having to re-execute these queries. Thanks to this, the database administrator can inspect the execution plans and decide if and where to apply indexes or perform a deeper analysis.
The auto-explain module is configured via a set of auto_explain parameter options that can be inserted in the PostgreSQL configuration (the postgresql.conf file), but you need to remember that in order to activate the module, you need to restart the cluster.
The auto-explain module can do pretty much the same things that a manual EXPLAIN command can do, including...