SET ROLE — set the current user identifier of the current session
SET [ SESSION | LOCAL ] ROLE role_name
SET [ SESSION | LOCAL ] ROLE NONE
RESET ROLE
   This command sets the current user
   identifier of the current SQL session to be role_name.  The role name can be
   written as either an identifier or a string literal.
   After SET ROLE, permissions checking for SQL commands
   is carried out as though the named role were the one that had logged
   in originally.
  
   The specified role_name
   must be a role that the current session user is a member of.
   (If the session user is a superuser, any role can be selected.)
  
   The SESSION and LOCAL modifiers act the same
   as for the regular SET
   command.
  
   The NONE and RESET forms reset the current
   user identifier to be the current session user identifier.
   These forms can be executed by any user.
  
   Using this command, it is possible to either add privileges or restrict
   one's privileges.  If the session user role has the INHERITS
   attribute, then it automatically has all the privileges of every role that
   it could SET ROLE to; in this case SET ROLE
   effectively drops all the privileges assigned directly to the session user
   and to the other roles it is a member of, leaving only the privileges
   available to the named role.  On the other hand, if the session user role
   has the NOINHERITS attribute, SET ROLE drops the
   privileges assigned directly to the session user and instead acquires the
   privileges available to the named role.
  
   In particular, when a superuser chooses to SET ROLE to a
   non-superuser role, they lose their superuser privileges.
  
   SET ROLE has effects comparable to
   SET SESSION AUTHORIZATION, but the privilege
   checks involved are quite different.  Also,
   SET SESSION AUTHORIZATION determines which roles are
   allowable for later SET ROLE commands, whereas changing
   roles with SET ROLE does not change the set of roles
   allowed to a later SET ROLE.
  
   SET ROLE does not process session variables as specified by
   the role's ALTER ROLE settings;  this only happens during
   login.
  
   SET ROLE cannot be used within a
   SECURITY DEFINER function.
  
SELECT SESSION_USER, CURRENT_USER; session_user | current_user --------------+-------------- peter | peter SET ROLE 'paul'; SELECT SESSION_USER, CURRENT_USER; session_user | current_user --------------+-------------- peter | paul
   PostgreSQL
   allows identifier syntax ("), while
   the SQL standard requires the role name to be written as a string
   literal.  SQL does not allow this command during a transaction;
   PostgreSQL does not make this
   restriction because there is no reason to.
   The rolename"SESSION and LOCAL modifiers are a
   PostgreSQL extension, as is the
   RESET syntax.