postgresql/doc/src/sgml/ref/set_role.sgml

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doc/src/sgml/ref/set_role.sgml
PostgreSQL documentation
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<refentry id="sql-set-role">
 <indexterm zone="sql-set-role">
  <primary>SET ROLE</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>SET ROLE</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>SET ROLE</refname>
  <refpurpose>set the current user identifier of the current session</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
SET [ SESSION | LOCAL ] ROLE <replaceable class="parameter">role_name</replaceable>
SET [ SESSION | LOCAL ] ROLE NONE
RESET ROLE
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   This command sets the current user
   identifier of the current SQL session to be <replaceable
   class="parameter">role_name</replaceable>.  The role name can be
   written as either an identifier or a string literal.
   After <command>SET ROLE</command>, permissions checking for SQL commands
   is carried out as though the named role were the one that had logged
   in originally.  Note that <command>SET ROLE</command> and
   <command>SET SESSION AUTHORIZATION</command> are exceptions; permissions
   checks for those continue to use the current session user and the initial
   session user (the <firstterm>authenticated user</firstterm>), respectively.
  </para>

  <para>
   The current session user must have the <literal>SET</literal> option for the
   specified <replaceable class="parameter">role_name</replaceable>, either
   directly or indirectly via a chain of memberships with the
   <literal>SET</literal> option.
   (If the session user is a superuser, any role can be selected.)
  </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>
   <literal>SET ROLE NONE</literal> sets the current user identifier to the
   current session user identifier, as returned by
   <function>session_user</function>.  <literal>RESET ROLE</literal> sets the
   current user identifier to the connection-time setting specified by the
   <link linkend="libpq-connect-options">command-line options</link>,
   <link linkend="sql-alterrole"><command>ALTER ROLE</command></link>, or
   <link linkend="sql-alterdatabase"><command>ALTER DATABASE</command></link>,
   if any such settings exist.  Otherwise, <literal>RESET ROLE</literal> sets
   the current user identifier to the current session user identifier.  These
   forms can be executed by any user.
  </para>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   Using this command, it is possible to either add privileges or restrict
   one's privileges.  If the session user role has been granted memberships
   <literal>WITH INHERIT TRUE</literal>, it automatically has all the
   privileges of every such role. In this case, <command>SET ROLE</command>
   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 <literal>WITH INHERIT FALSE</literal>, the
   privileges of the granted roles can't be accessed by default. However, if
   the role was granted <literal>WITH SET TRUE</literal>, the
   session user can use <command>SET ROLE</command> 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 <literal>WITH INHERIT
   FALSE, SET FALSE</literal> then the privileges of that role cannot be
   exercised either with or without <literal>SET ROLE</literal>.
  </para>

  <para>
   <command>SET ROLE</command> has effects comparable to
   <link linkend="sql-set-session-authorization"><command>SET SESSION AUTHORIZATION</command></link>, but the privilege
   checks involved are quite different.  Also,
   <command>SET SESSION AUTHORIZATION</command> determines which roles are
   allowable for later <command>SET ROLE</command> commands, whereas changing
   roles with <command>SET ROLE</command> does not change the set of roles
   allowed to a later <command>SET ROLE</command>.
  </para>

  <para>
   <command>SET ROLE</command> does not process session variables as specified by
   the role's <link linkend="sql-alterrole"><command>ALTER ROLE</command></link> settings;  this only happens during
   login.
  </para>

  <para>
   <command>SET ROLE</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 ROLE 'paul';

SELECT SESSION_USER, CURRENT_USER;

 session_user | current_user
--------------+--------------
 peter        | paul
</programlisting>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <productname>PostgreSQL</productname>
   allows identifier syntax (<literal>"<replaceable>rolename</replaceable>"</literal>), while
   the SQL standard requires the role name to be written as a string
   literal.  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>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-set-session-authorization"/></member>
  </simplelist>
 </refsect1>
</refentry>