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<!--
doc/src/sgml/ref/set_session_auth.sgml
PostgreSQL documentation
-->
<refentry id="sql-set-session-authorization">
<indexterm zone="sql-set-session-authorization">
<primary>SET SESSION AUTHORIZATION</primary>
</indexterm>
<refmeta>
<refentrytitle>SET SESSION AUTHORIZATION</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>SET SESSION AUTHORIZATION</refname>
<refpurpose>set the session user identifier and the current user identifier of the current session</refpurpose>
</refnamediv>
<refsynopsisdiv>
<synopsis>
SET [ SESSION | LOCAL ] SESSION AUTHORIZATION <replaceable class="parameter">user_name</replaceable>
SET [ SESSION | LOCAL ] SESSION AUTHORIZATION DEFAULT
RESET SESSION AUTHORIZATION
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
This command sets the session user identifier and the current user
identifier of the current SQL session to be <replaceable
class="parameter">user_name</replaceable>. 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.
</para>
<para>
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 <literal>SECURITY DEFINER</literal>
functions and similar mechanisms; it can also be changed by
<link linkend="sql-set-role"><command>SET ROLE</command></link>.
The current user identifier is relevant for permission checking.
</para>
<para>
The session user identifier can be changed only if the initial session
user (the <firstterm>authenticated user</firstterm>) had the
superuser privilege. Otherwise, the command is accepted only if it
specifies the authenticated user name.
</para>
<para>
The <literal>SESSION</literal> and <literal>LOCAL</literal> modifiers act the same
as for the regular <link linkend="sql-set"><command>SET</command></link>
command.
</para>
<para>
The <literal>DEFAULT</literal> and <literal>RESET</literal> forms reset the session
and current user identifiers to be the originally authenticated user
name. These forms can be executed by any user.
</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
<command>SET SESSION AUTHORIZATION</command> cannot be used within a
<literal>SECURITY DEFINER</literal> function.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<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
</programlisting>
</refsect1>
<refsect1>
<title>Compatibility</title>
<para>
The SQL standard allows some other expressions to appear in place
of the literal <replaceable>user_name</replaceable>, but these options
are not important in practice. <productname>PostgreSQL</productname>
allows identifier syntax (<literal>"<replaceable>username</replaceable>"</literal>), which SQL
does not. SQL does not allow this command during a transaction;
<productname>PostgreSQL</productname> does not make this
restriction because there is no reason to.
The <literal>SESSION</literal> and <literal>LOCAL</literal> modifiers are a
<productname>PostgreSQL</productname> extension, as is the
<literal>RESET</literal> syntax.
</para>
<para>
The privileges necessary to execute this command are left
implementation-defined by the standard.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-set-role"/></member>
</simplelist>
</refsect1>
</refentry>
|
