redhat man page for set_session_authorization

SET SESSION 
AUTHORIZATION(7)					   SQL Commands 				      SET SESSION AUTHORIZATION(7)

NAME
       SET SESSION AUTHORIZATION - set the session user identifier and the current user identifier of the current session

SYNOPSIS
       SET [ SESSION | LOCAL ] SESSION AUTHORIZATION username
       SET [ SESSION | LOCAL ] SESSION AUTHORIZATION DEFAULT
       RESET SESSION AUTHORIZATION

DESCRIPTION
       This  command  sets the session user identifier and the current user identifier of the current SQL-session context to be username. The user
       name may be written as either an identifier or a string literal.  The session user identifier is valid for the duration	of  a  connection;
       for example, it is possible to temporarily become an unprivileged user and later switch back to become a superuser.

       The  session user identifier is initially set to be the (possibly authenticated) user name provided by the client. The current user identi-
       fier is normally equal to the session user identifier, but may change temporarily in the context of ``setuid'' functions and similar mecha-
       nisms. The current user identifier is relevant for permission checking.

       The  session  user  identifier may be changed only if the initial session user (the authenticated user) had the superuser privilege. Other-
       wise, the command is accepted only if it specifies the authenticated user name.

       The SESSION and LOCAL modifiers act the same as for the regular SET [set(7)] command.

       The DEFAULT and RESET forms reset the session and current user identifiers to be the originally authenticated user name.  These	forms  are
       always accepted.

EXAMPLES
       SELECT SESSION_USER, CURRENT_USER;
	current_user | session_user
       --------------+--------------
	peter	     | peter

       SET SESSION AUTHORIZATION 'paul';

       SELECT SESSION_USER, CURRENT_USER;
	current_user | session_user
       --------------+--------------
	paul	     | paul

COMPATIBILITY
       SQL99

       SQL99 allows some other expressions to appear in place of the literal username which are not important in practice. PostgreSQL allows iden-
       tifier syntax ("username"), which SQL does not. SQL does not allow this command	during	a  transaction;  PostgreSQL  does  not	make  this
       restriction  because  there  is no reason to. The privileges necessary to execute this command are left implementation-defined by the stan-
       dard.

SQL - Language Statements					    2001-04-21					      SET SESSION AUTHORIZATION(7)