Checking whether a user is connected

Here, we will show you how to learn whether a certain database user is currently connected to the database.

Getting ready

If you are logged in as a superuser, you will have full access to monitoring information.

How to do it…

Issue the following query to see whether the user bob is connected:

SELECT datname FROM pg_stat_activity WHERE usename = 'bob';

If this query returns any rows, then that means that bob is connected to the database. The returned value is the name of the database that the user is connected to.

How it works…

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 each backend, who is connected, when the connection, the transaction, and/or the query were started, and so on...