Here, we will show you how to learn whether a certain database user is currently connected to the database.
Make sure that you are logged in as a superuser.
Issue the following query to see whether the
bob user is connected:
SELECT datname FROM pg_stat_activity WHERE usename = 'bob';
If this query returns any rows, then it means
bob is connected to the database. The returned value is the name of the database to which the user is connected.
pg_stat_activity system view keeps track of all running PostgreSQL backends. This includes information such as the query that is being currently executed (or the last query that was executed by a backend—available from 9.2); ...