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$PostgreSQL: pgsql/doc/src/sgml/ref/alter_function.sgml,v 1.16 2008/07/16 01:30:21 tgl Exp $
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<refentry id="SQL-ALTERFUNCTION">
 <refmeta>
  <refentrytitle id="SQL-ALTERFUNCTION-TITLE">ALTER FUNCTION</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>ALTER FUNCTION</refname>
  <refpurpose>change the definition of a function</refpurpose>
 </refnamediv>  
  
 <indexterm zone="sql-alterfunction">
  <primary>ALTER FUNCTION</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
    <replaceable class="PARAMETER">action</replaceable> [ ... ] [ RESTRICT ]
ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
    RENAME TO <replaceable>new_name</replaceable>
ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
    OWNER TO <replaceable>new_owner</replaceable>
ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
    SET SCHEMA <replaceable>new_schema</replaceable>

where <replaceable class="PARAMETER">action</replaceable> is one of:

    CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT
    IMMUTABLE | STABLE | VOLATILE
    [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
    COST <replaceable class="parameter">execution_cost</replaceable>
    ROWS <replaceable class="parameter">result_rows</replaceable>
    SET <replaceable class="parameter">configuration_parameter</replaceable> { TO | = } { <replaceable class="parameter">value</replaceable> | DEFAULT }
    SET <replaceable class="parameter">configuration_parameter</replaceable> FROM CURRENT
    RESET <replaceable class="parameter">configuration_parameter</replaceable>
    RESET ALL
</synopsis>
 </refsynopsisdiv>
  
 <refsect1>
  <title>Description</title>

  <para>
   <command>ALTER FUNCTION</command> changes the definition of a
   function.
  </para>

  <para>
   You must own the function to use <command>ALTER FUNCTION</>.
   To change a function's schema, you must also have <literal>CREATE</>
   privilege on the new schema.
   To alter the owner, you must also be a direct or indirect member of the new
   owning role, and that role must have <literal>CREATE</literal> privilege on
   the function's schema.  (These restrictions enforce that altering the owner
   doesn't do anything you couldn't do by dropping and recreating the function.
   However, a superuser can alter ownership of any function anyway.)
  </para>
 </refsect1>
  
 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing function.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argmode</replaceable></term>

    <listitem>
     <para>
      The mode of an argument: <literal>IN</>, <literal>OUT</>,
      <literal>INOUT</>, or <literal>VARIADIC</>.
      If omitted, the default is <literal>IN</>.
      Note that <command>ALTER FUNCTION</command> does not actually pay
      any attention to <literal>OUT</> arguments, since only the input
      arguments are needed to determine the function's identity.
      So it is sufficient to list the <literal>IN</>, <literal>INOUT</>,
      and <literal>VARIADIC</> arguments.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argname</replaceable></term>

    <listitem>
     <para>
      The name of an argument.
      Note that <command>ALTER FUNCTION</command> does not actually pay
      any attention to argument names, since only the argument data
      types are needed to determine the function's identity.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argtype</replaceable></term>

    <listitem>
     <para>
      The data type(s) of the function's arguments (optionally 
      schema-qualified), if any.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_name</replaceable></term>
    <listitem>
     <para>
      The new name of the function.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_owner</replaceable></term>
    <listitem>
     <para>
      The new owner of the function.  Note that if the function is
      marked <literal>SECURITY DEFINER</literal>, it will subsequently
      execute as the new owner.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_schema</replaceable></term>
    <listitem>
     <para>
      The new schema for the function.
     </para>
    </listitem>
   </varlistentry>

    <varlistentry>
     <term><literal>CALLED ON NULL INPUT</literal></term>
     <term><literal>RETURNS NULL ON NULL INPUT</literal></term>
     <term><literal>STRICT</literal></term>

     <listitem>
      <para>
       <literal>CALLED ON NULL INPUT</literal> changes the function so
       that it will be invoked when some or all of its arguments are
       null. <literal>RETURNS NULL ON NULL INPUT</literal> or
       <literal>STRICT</literal> changes the function so that it is not
       invoked if any of its arguments are null; instead, a null result
       is assumed automatically.  See <xref linkend="sql-createfunction"
       endterm="sql-createfunction-title"> for more information.
      </para>
     </listitem>
   </varlistentry>

    <varlistentry>
     <term><literal>IMMUTABLE</literal></term>
     <term><literal>STABLE</literal></term>
     <term><literal>VOLATILE</literal></term>

     <listitem>
      <para>
       Change the volatility of the function to the specified setting.
       See <xref linkend="sql-createfunction"
       endterm="sql-createfunction-title"> for details.
      </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal><optional> EXTERNAL </optional> SECURITY INVOKER</literal></term>
    <term><literal><optional> EXTERNAL </optional> SECURITY DEFINER</literal></term>

    <listitem>
     <para>
      Change whether the function is a security definer or not. The
      key word <literal>EXTERNAL</literal> is ignored for SQL
      conformance. See <xref linkend="sql-createfunction"
      endterm="sql-createfunction-title"> for more information about
      this capability.
     </para>
    </listitem>
   </varlistentry>

    <varlistentry>
     <term><literal>COST</literal> <replaceable class="parameter">execution_cost</replaceable></term>

     <listitem>
      <para>
       Change the estimated execution cost of the function.
       See <xref linkend="sql-createfunction"
       endterm="sql-createfunction-title"> for more information.
      </para>
     </listitem>
   </varlistentry>

    <varlistentry>
     <term><literal>ROWS</literal> <replaceable class="parameter">result_rows</replaceable></term>

     <listitem>
      <para>
       Change the estimated number of rows returned by a set-returning
       function.  See <xref linkend="sql-createfunction"
       endterm="sql-createfunction-title"> for more information.
      </para>
     </listitem>
   </varlistentry>

     <varlistentry>
      <term><replaceable>configuration_parameter</replaceable></term>
      <term><replaceable>value</replaceable></term>
      <listitem>
       <para>
        Add or change the assignment to be made to a configuration parameter
        when the function is called.  If
        <replaceable>value</replaceable> is <literal>DEFAULT</literal>
        or, equivalently, <literal>RESET</literal> is used, the function-local
        setting is removed, so that the function executes with the value
        present in its environment.  Use <literal>RESET
        ALL</literal> to clear all function-local settings.
        <literal>SET FROM CURRENT</> saves the session's current value of
        the parameter as the value to be applied when the function is entered.
       </para>

       <para>
        See <xref linkend="sql-set" endterm="sql-set-title"> and
        <xref linkend="runtime-config">
        for more information about allowed parameter names and values.
       </para>
      </listitem>
     </varlistentry>

   <varlistentry>
    <term><literal>RESTRICT</literal></term>

    <listitem>
     <para>
      Ignored for conformance with the SQL standard.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   To rename the function <literal>sqrt</literal> for type
   <type>integer</type> to <literal>square_root</literal>:
<programlisting>
ALTER FUNCTION sqrt(integer) RENAME TO square_root;
</programlisting>
  </para>

  <para>
   To change the owner of the function <literal>sqrt</literal> for type
   <type>integer</type> to <literal>joe</literal>:
<programlisting>
ALTER FUNCTION sqrt(integer) OWNER TO joe;
</programlisting>
  </para>

  <para>
   To change the schema of the function <literal>sqrt</literal> for type
   <type>integer</type> to <literal>maths</literal>:
<programlisting>
ALTER FUNCTION sqrt(integer) SET SCHEMA maths;
</programlisting>
  </para>

  <para>
   To adjust the search path that is automatically set for a function:
<programlisting>
ALTER FUNCTION check_password(text) SET search_path = admin, pg_temp;
</programlisting>
  </para>

  <para>
   To disable automatic setting of <varname>search_path</> for a function:
<programlisting>
ALTER FUNCTION check_password(text) RESET search_path;
</programlisting>
   The function will now execute with whatever search path is used by its
   caller.
  </para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   This statement is partially compatible with the <command>ALTER
   FUNCTION</> statement in the SQL standard. The standard allows more
   properties of a function to be modified, but does not provide the
   ability to rename a function, make a function a security definer,
   attach configuration parameter values to a function,
   or change the owner, schema, or volatility of a function. The standard also
   requires the <literal>RESTRICT</> key word, which is optional in
   <productname>PostgreSQL</>.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createfunction" endterm="sql-createfunction-title"></member>
   <member><xref linkend="sql-dropfunction" endterm="sql-dropfunction-title"></member>
  </simplelist>
 </refsect1>
</refentry>
