PostgreSQL 11 Administration Cookbook

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PostgreSQL provides a version of the pg_stat_activity view that's capable of capturing many kinds of waits; however, in older versions, pg_stat_activity could only detect waits on locks such as those placed on SQL objects, via the pg_stat_activity.waiting field.

Although this is the main cause of waiting when using pure SQL, it is possible to write a query in any of PostgreSQL's embedded languages that can wait on other system resources, such as waiting for an HTTP response, for a file write to get completed, or just waiting on a timer.

As an example, you can make your backend sleep for a certain number of seconds using pg_sleep(seconds). While you are monitoring pg_stat_activity, open a new Terminal session with psql and run ...