Returns the user name of the current "effective" user of the database, as applicable to checking permissions. Usually, this user name will be the same as the session user; however, this can occasionally be changed by superusers.
Do not use trailing parentheses when calling CURRENT_USER.
CURRENT_USER returns a CHAR or VARCHAR string.
The following query returns the name of the current database user:
select current_user; current_user -------------- dwuser (1 row)