SET ROLE {
    DEFAULT
  | NONE
  | ALL
  | ALL EXCEPT role [, role ] ...
  | role [, role ] ...
}
        SET ROLE modifies the current
        user's effective privileges within the current session by
        specifying which of its granted roles are active. Granted roles
        include those granted explicitly to the user and those named in
        the mandatory_roles system
        variable value.
      
Examples:
SET ROLE DEFAULT;
SET ROLE 'role1', 'role2';
SET ROLE ALL;
SET ROLE ALL EXCEPT 'role1', 'role2';
        Each role name uses the format described in
        Section 8.2.5, “Specifying Role Names”. The host name part of the role
        name, if omitted, defaults to '%'.
      
Privileges that the user has been granted directly (rather than through roles) remain unaffected by changes to the active roles.
The statement permits these role specifiers:
- DEFAULT: Activate the account default roles. Default roles are those specified with- SET DEFAULT ROLE.- When a user connects to the server and authenticates successfully, the server determines which roles to activate as the default roles. If the - activate_all_roles_on_loginsystem variable is enabled, the server activates all granted roles. Otherwise, the server executes- SET ROLE DEFAULTimplicitly. The server activates only default roles that can be activated. The server writes warnings to its error log for default roles that cannot be activated, but the client receives no warnings.- If a user executes - SET ROLE DEFAULTduring a session, an error occurs if any default role cannot be activated (for example, if it does not exist or is not granted to the user). In this case, the current active roles are not changed.
- NONE: Set the active roles to- NONE(no active roles).
- ALL: Activate all roles granted to the account.
- ALL EXCEPT: Activate all roles granted to the account except those named. The named roles need not exist or be granted to the account.- role[,- role] ...
- role[,- role] ...
          SET DEFAULT ROLE and
          SET ROLE
          DEFAULT are different statements:
- SET DEFAULT ROLEdefines which account roles to activate by default within account sessions.
- SET ROLE DEFAULTsets the active roles within the current session to the current account default roles.
For role usage examples, see Section 8.2.10, “Using Roles”.