<literal>OUT</literal> are just noise.  But
   writing them is recommendable for consistency with the
   corresponding <command>CREATE</command> command.
  </para>

  <para>
   For compatibility with the SQL standard, it is also allowed to write
   all the argument data types (including those of <literal>OUT</literal>
   arguments) without
   any <replaceable class="parameter">argmode</replaceable> markers.
   When this is done, the types of the procedure's <literal>OUT</literal>
   argument(s) <emphasis>will</emphasis> be verified against the command.
   This provision creates an ambiguity, in that when the argument list
   contains no <replaceable class="parameter">argmode</replaceable>
   markers, it's unclear which rule is intended.
   The <command>DROP</command> command will attempt the lookup both ways,
   and will throw an error if two different procedures are found.
   To avoid the risk of such ambiguity, it's recommendable to
   write <literal>IN</literal> markers explicitly rather than letting them
   be defaulted, thus forcing the
   traditional <productname>PostgreSQL</productname> interpretation to be
   used.
  </para>

  <para>
   The lookup rules just explained are also used by other commands that
   act on existing procedures, such as <command>ALTER PROCEDURE</command>
   and <command>COMMENT ON PROCEDURE</command>.
  </para>
 </refsect1>

 <refsect1 id="sql-dropprocedure-examples">
  <title>Examples</title>

  <para>
   If there is only one procedure <literal>do_db_maintenance</literal>,
   this command is sufficient to drop it:
<programlisting>
DROP PROCEDURE do_db_maintenance;
</programlisting>
  </para>

  <para>
   Given this procedure definition:
<programlisting>
CREATE PROCEDURE do_db_maintenance(IN target_schema text, OUT results text) ...
</programlisting>
   any one of these commands would work to drop it:
<programlisting>
DROP PROCEDURE do_db_maintenance(IN target_schema text, OUT results text);
DROP PROCEDURE do_db_maintenance(IN text, OUT text);
DROP PROCEDURE do_db_maintenance(IN text);
DROP PROCEDURE do_db_maintenance(text);
DROP PROCEDURE do_db_maintenance(text, text);  -- potentially ambiguous
</programlisting>
   However, the last example would be ambiguous if there is also, say,
<programlisting>
CREATE PROCEDURE do_db_maintenance(IN target_schema text, IN options text) ...
</programlisting></para>
 </refsect1>

 <refsect1 id="sql-dropprocedure-compatibility">
  <title>Compatibility</title>

  <para>
   This command conforms to the SQL standard, with
   these <productname>PostgreSQL</productname> extensions:
   <itemizedlist>
    <listitem>
     <para>The standard only allows one procedure to be dropped per command.</para>
    </listitem>
    <listitem>
     <para>The <literal>IF EXISTS</literal> option is an extension.</para>
    </listitem>
    <listitem>
     <para>The ability to specify argument modes and names is an
     extension, and the lookup rules differ when modes are given.</para>
    </listitem>
   </itemizedlist></para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createprocedure"/></member>
   <member><xref linkend="sql-alterprocedure"/></member>
   <member><xref linkend="sql-dropfunction"/></member>
   <member><xref linkend="sql-droproutine"/></member>
  </simplelist>
 </refsect1>

</refentry>