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3rd chunk of `doc/src/sgml/ref/create_foreign_data_wrapper.sgml`
ba489229999ea3a78f643fd51cff2f56c15a35e1723697480000000100000bd1
 specifications at run time,
      depending on the implementation.)  The validator function must
      take two arguments: one of type <type>text[]</type>, which will
      contain the array of options as stored in the system catalogs,
      and one of type <type>oid</type>, which will be the OID of the
      system catalog containing the options. The return type is ignored;
      the function should report invalid options using the
      <function>ereport(ERROR)</function> function.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>OPTIONS ( <replaceable class="parameter">option</replaceable> '<replaceable class="parameter">value</replaceable>' [, ... ] )</literal></term>
    <listitem>
     <para>
      This clause specifies options for the new foreign-data wrapper.
      The allowed option names and values are specific to each foreign
      data wrapper and are validated using the foreign-data wrapper's
      validator function.  Option names must be unique.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   <productname>PostgreSQL</productname>'s foreign-data functionality is still under
   active development.  Optimization of queries is primitive (and mostly left
   to the wrapper, too).  Thus, there is considerable room for future
   performance improvements.
  </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   Create a useless foreign-data wrapper <literal>dummy</literal>:
<programlisting>
CREATE FOREIGN DATA WRAPPER dummy;
</programlisting>
  </para>

  <para>
   Create a foreign-data wrapper <literal>file</literal> with
   handler function <literal>file_fdw_handler</literal>:
<programlisting>
CREATE FOREIGN DATA WRAPPER file HANDLER file_fdw_handler;
</programlisting>
  </para>

  <para>
   Create a foreign-data wrapper <literal>mywrapper</literal> with some
   options:
<programlisting>
CREATE FOREIGN DATA WRAPPER mywrapper
    OPTIONS (debug 'true');
</programlisting></para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <command>CREATE FOREIGN DATA WRAPPER</command> conforms to ISO/IEC
   9075-9 (SQL/MED), with the exception that the <literal>HANDLER</literal>
   and <literal>VALIDATOR</literal> clauses are extensions and the standard
   clauses <literal>LIBRARY</literal> and <literal>LANGUAGE</literal>
   are not implemented in <productname>PostgreSQL</productname>.
  </para>

  <para>
   Note, however, that the SQL/MED functionality as a whole is not yet
   conforming.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-alterforeigndatawrapper"/></member>
   <member><xref linkend="sql-dropforeigndatawrapper"/></member>
   <member><xref linkend="sql-createserver"/></member>
   <member><xref linkend="sql-createusermapping"/></member>
   <member><xref linkend="sql-createforeigntable"/></member>
  </simplelist>
 </refsect1>

</refentry>
Title: CREATE FOREIGN DATA WRAPPER Notes, Examples, Compatibility, and See Also
Summary
This section covers additional information about `CREATE FOREIGN DATA WRAPPER`. It includes notes on the ongoing development and optimization of PostgreSQL's foreign-data functionality. It provides examples of creating foreign-data wrappers with and without handler functions and options. It also discusses the command's compatibility with the SQL/MED standard, noting extensions and unimplemented clauses. Finally, it lists related SQL commands such as ALTER FOREIGN DATA WRAPPER, DROP FOREIGN DATA WRAPPER, CREATE SERVER, CREATE USER MAPPING and CREATE FOREIGN TABLE.