Here, we will show you how to learn whether a certain database user is currently connected to the database.
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.
PostgreSQL's 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); who is connected; when the connection, the transaction, and/or the query were started; and so on.