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><H1
><A
NAME="SQL-SET-SESSION-AUTHORIZATION"
></A
>SET SESSION AUTHORIZATION</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN78997"
></A
><H2
>Name</H2
>SET SESSION AUTHORIZATION&nbsp;--&nbsp;set the session user identifier and the current user identifier of the current session</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN79002"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>SET [ SESSION | LOCAL ] SESSION AUTHORIZATION <TT
CLASS="REPLACEABLE"
><I
>user_name</I
></TT
>
SET [ SESSION | LOCAL ] SESSION AUTHORIZATION DEFAULT
RESET SESSION AUTHORIZATION</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN79005"
></A
><H2
>Description</H2
><P
>   This command sets the session user identifier and the current user
   identifier of the current SQL session to be <TT
CLASS="REPLACEABLE"
><I
>user_name</I
></TT
>.  The user name can be
   written as either an identifier or a string literal.  Using this
   command, it is possible, for example, to temporarily become an
   unprivileged user and later switch back to being a superuser.
  </P
><P
>   The session user identifier is initially set to be the (possibly
   authenticated) user name provided by the client.  The current user
   identifier is normally equal to the session user identifier, but
   might change temporarily in the context of <TT
CLASS="LITERAL"
>SECURITY DEFINER</TT
>
   functions and similar mechanisms; it can also be changed by
   <A
HREF="sql-set-role.html"
>SET ROLE</A
>.
   The current user identifier is relevant for permission checking.
  </P
><P
>   The session user identifier can be changed only if the initial session
   user (the <I
CLASS="FIRSTTERM"
>authenticated user</I
>) had the
   superuser privilege.  Otherwise, the command is accepted only if it
   specifies the authenticated user name.
  </P
><P
>   The <TT
CLASS="LITERAL"
>SESSION</TT
> and <TT
CLASS="LITERAL"
>LOCAL</TT
> modifiers act the same
   as for the regular <A
HREF="sql-set.html"
>SET</A
>
   command.
  </P
><P
>   The <TT
CLASS="LITERAL"
>DEFAULT</TT
> and <TT
CLASS="LITERAL"
>RESET</TT
> forms reset the session
   and current user identifiers to be the originally authenticated user
   name.  These forms can be executed by any user.
  </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN79021"
></A
><H2
>Notes</H2
><P
>   <TT
CLASS="COMMAND"
>SET SESSION AUTHORIZATION</TT
> cannot be used within a
   <TT
CLASS="LITERAL"
>SECURITY DEFINER</TT
> function.
  </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN79026"
></A
><H2
>Examples</H2
><PRE
CLASS="PROGRAMLISTING"
>SELECT SESSION_USER, CURRENT_USER;

 session_user | current_user 
--------------+--------------
 peter        | peter

SET SESSION AUTHORIZATION 'paul';

SELECT SESSION_USER, CURRENT_USER;

 session_user | current_user 
--------------+--------------
 paul         | paul</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN79029"
></A
><H2
>Compatibility</H2
><P
>   The SQL standard allows some other expressions to appear in place
   of the literal <TT
CLASS="REPLACEABLE"
><I
>user_name</I
></TT
>, but these options
   are not important in practice.  <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
   allows identifier syntax (<TT
CLASS="LITERAL"
>"username"</TT
>), which SQL
   does not.  SQL does not allow this command during a transaction;
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> does not make this
   restriction because there is no reason to.
   The <TT
CLASS="LITERAL"
>SESSION</TT
> and <TT
CLASS="LITERAL"
>LOCAL</TT
> modifiers are a
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> extension, as is the
   <TT
CLASS="LITERAL"
>RESET</TT
> syntax.
  </P
><P
>   The privileges necessary to execute this command are left
   implementation-defined by the standard.
  </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN79041"
></A
><H2
>See Also</H2
><A
HREF="sql-set-role.html"
>SET ROLE</A
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