In this post, I am sharing a script for transforming normal DB user to Super User in PostgreSQL.

The Super User is the admin user and it has all kind of access to PostgreSQL Server. We can create multiple superusers in PostgreSQL.

I need this kind of handy commands/scripts because when any new dba join the team, giving basic permission of database and later the same user requires superuser permission.

Convert a user into Super User:

ALTER USER user_name WITH SUPERUSER;

Revoke Super User Permission:

ALTER USER user_name WITH NOSUPERUSER;

Few weeks ago, We got an error in one of our client PostgreSQL Server. Below is an error:
psql.bin: FATAL: remaining connection slots are reserved for non-replication superuser connections

The solution of above error is also very straightforward and short. You are getting this error because your server exceeded the limit of max_connections parameter.max_connection.

The solution is:

Increase the value of [max_connections] parameter:

Decrease the value of [superuser_reserved_connections] parameter:

You can find above both parameters in postgresql.conf file.
Note: After changing parameters, you must restart the PostgreSQL cluster.

In this post, I am sharing a UDF and using this non-super user can kill their queries.

As a PostgreSQL DBA, You may find long running queries or IDLE queries of the user. Many times users also disturb to DBA for killing their queries.

In my organisation, we created one function and assigned to all users so that they can kill their queries without disturbing to DBA team.

This function created such a way that, a user can kill their own queries only. They can find process_id of other users, but they can’t kill other queries.

Below is a full demonstration of this:

Create a schema:

CREATE SCHEMA query_admin;

Create a function to kill user query:

CREATE OR REPLACE FUNCTION query_admin.kill_process(userpid integer)
RETURNS boolean AS $body$
DECLARE
    qry boolean;
BEGIN
    qry := (SELECT pg_catalog.pg_cancel_backend(pid) 
            FROM pg_stat_activity 
            WHERE usename=(select session_user) 
            AND pid=userpid);
    RETURN qry;
END;
$body$
LANGUAGE plpgsql
SECURITY DEFINER
VOLATILE
RETURNS NULL ON NULL INPUT;

Grant permission to Public so that all user can access this:

GRANT USAGE ON SCHEMA query_admin TO public;
GRANT EXECUTE ON FUNCTION query_admin.kill_process(pid integer) TO public;

User can check their running process_id queries using below query:

SELECT * FROM pg_stat_activity 
WHERE usename = 'user_name';

Sample execution of kill_process():

SELECT *FROM query_admin.kill_process(process_id);
SELECT *FROM query_admin.kill_process(14526);