Please, consider this small fix for the query example in the docs[1]:
SELECT a.pid, a.wait_event, w.description FROM pg_stat_activity a JOIN pg_wait_events w ON (a.wait_event_type = w.type AND a.wait_event = w.name) WHERE wait_event is NOT NULL and a.state = 'active';
I propose to add a table alias for the wait_event column in the WHERE clause for consistency.
1. https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW
