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

  <para>
   You must own the function to use <command>ALTER FUNCTION</command>.
   To change a function's schema, you must also have <literal>CREATE</literal>
   privilege on the new schema.  To alter the owner, you must be able to
   <literal>SET ROLE</literal> to 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.  If no
      argument list is specified, the name must be unique in its schema.
     </para>
    </listitem>
   </varlistentry>

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

    <listitem>
     <para>
      The mode of an argument: <literal>IN</literal>, <literal>OUT</literal>,
      <literal>INOUT</literal>, or <literal>VARIADIC</literal>.
      If omitted, the default is <literal>IN</literal>.
      Note that <command>ALTER FUNCTION</command> does not actually pay
      any attention to <literal>OUT</literal> arguments, since only the input
      arguments are needed to determine the function's identity.
      So it is sufficient to list the <literal>IN</literal>, <literal>INOUT</literal>,
      and <literal>VARIADIC</literal> 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>DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
    <term><literal>NO DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
    <listitem>
     <para>
      This form marks the function as dependent on the extension, or no longer
      dependent on that extension if <literal>NO</literal> is specified.
      A function that's marked as dependent on an extension is dropped when the
      extension is dropped, even if <literal>CASCADE</literal> is not specified.
      A function can depend upon multiple extensions, and will be dropped when
      any one of those extensions is dropped.
     </para>
    </listitem>
   </varlistentry>

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