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.  Note that SET ROLE and
   SET SESSION AUTHORIZATION are exceptions; permissions
   checks for those continue to use the current session user and the initial
   session user (the authenticated user), respectively.
  
   The current session user must have the SET option for the
   specified role_name, either
   directly or indirectly via a chain of memberships with the
   SET option.
   (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.
  
   SET ROLE NONE sets the current user identifier to the
   current session user identifier, as returned by
   session_user.  RESET ROLE sets the
   current user identifier to the connection-time setting specified by the
   command-line options,
   ALTER ROLE, or
   ALTER DATABASE,
   if any such settings exist.  Otherwise, RESET ROLE sets
   the current user identifier to 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 been granted memberships
   WITH INHERIT TRUE, it automatically has all the
   privileges of every such role. In this case, SET ROLE
   effectively drops all the privileges except for those which the target role
   directly possesses or inherits.  On the other hand, if the session user role
   has been granted memberships WITH INHERIT FALSE, the
   privileges of the granted roles can't be accessed by default. However, if
   the role was granted WITH SET TRUE, the
   session user can use SET ROLE to drop the privileges
   assigned directly to the session user and instead acquire the privileges
   available to the named role. If the role was granted WITH INHERIT
   FALSE, SET FALSE then the privileges of that role cannot be
   exercised either with or without SET ROLE.
  
   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.