When executing "SELECT * FROM pg_stat_activity" I get lots of rows that
have an empty "query" column.
According to [1] this column should contain the "Text of this backend's
most recent query", either a query that is currently running or the last
query that was executed.
So how comes that a lot of the rows in pg_stat_activity have an empty
"query"?
https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW
