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
Make sure that you are logged in as a superuser.
How to do it…
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.
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 a backend—available from 9.2); ...
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