<!--
doc/src/sgml/ref/alter_foreign_data_wrapper.sgml
PostgreSQL documentation
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<refentry id="sql-alterforeigndatawrapper">
 <indexterm zone="sql-alterforeigndatawrapper">
  <primary>ALTER FOREIGN DATA WRAPPER</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>ALTER FOREIGN DATA WRAPPER</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>ALTER FOREIGN DATA WRAPPER</refname>
  <refpurpose>change the definition of a foreign-data wrapper</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
ALTER FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable>
    [ HANDLER <replaceable class="parameter">handler_function</replaceable> | NO HANDLER ]
    [ VALIDATOR <replaceable class="parameter">validator_function</replaceable> | NO VALIDATOR ]
    [ OPTIONS ( [ ADD | SET | DROP ] <replaceable class="parameter">option</replaceable> ['<replaceable class="parameter">value</replaceable>'] [, ... ]) ]
ALTER FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable> OWNER TO { <replaceable>new_owner</replaceable> | CURRENT_USER | SESSION_USER }
ALTER FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable> RENAME TO <replaceable>new_name</replaceable>
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>ALTER FOREIGN DATA WRAPPER</command> changes the
   definition of a foreign-data wrapper.  The first form of the
   command changes the support functions or the generic options of the
   foreign-data wrapper (at least one clause is required).  The second
   form changes the owner of the foreign-data wrapper.
  </para>

  <para>
   Only superusers can alter foreign-data wrappers.  Additionally,
   only superusers can own foreign-data wrappers.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name of an existing foreign-data wrapper.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>HANDLER <replaceable class="parameter">handler_function</replaceable></literal></term>
    <listitem>
     <para>
      Specifies a new handler function for the foreign-data wrapper.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>NO HANDLER</literal></term>
    <listitem>
     <para>
      This is used to specify that the foreign-data wrapper should no
      longer have a handler function.
     </para>
     <para>
      Note that foreign tables that use a foreign-data wrapper with no
      handler cannot be accessed.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>VALIDATOR <replaceable class="parameter">validator_function</replaceable></literal></term>
    <listitem>
     <para>
      Specifies a new validator function for the foreign-data wrapper.
     </para>

     <para>
      Note that it is possible that pre-existing options of the foreign-data
      wrapper, or of dependent servers, user mappings, or foreign tables, are
      invalid according to the new validator.  <productname>PostgreSQL</productname> does
      not check for this.  It is up to the user to make sure that these
      options are correct before using the modified foreign-data wrapper.
      However, any options specified in this <command>ALTER FOREIGN DATA
      WRAPPER</command> command will be checked using the new validator.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>NO VALIDATOR</literal></term>
    <listitem>
     <para>
      This is used to specify that the foreign-data wrapper should no
      longer have a validator function.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>OPTIONS ( [ ADD | SET | DROP ] <replaceable class="parameter">option</replaceable> ['<replaceable class="parameter">value</replaceable>'] [, ... ] )</literal></term>
    <listitem>
     <para>
      Change options for the foreign-data
      wrapper.  <literal>ADD</literal>, <literal>SET</literal>, and <literal>DROP</literal>
      specify the action to be performed.  <literal>ADD</literal> is assumed
      if no operation is explicitly specified.  Option names must be
      unique; names and values are also validated using the foreign
      data wrapper's validator function, if any.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_owner</replaceable></term>
    <listitem>
     <para>
      The user name of the new owner of the foreign-data wrapper.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_name</replaceable></term>
    <listitem>
     <para>
      The new name for the foreign-data wrapper.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   Change a foreign-data wrapper <literal>dbi</literal>, add
   option <literal>foo</literal>, drop <literal>bar</literal>:
<programlisting>
ALTER FOREIGN DATA WRAPPER dbi OPTIONS (ADD foo '1', DROP 'bar');
</programlisting>
  </para>

  <para>
   Change the foreign-data wrapper <literal>dbi</literal> validator
   to <literal>bob.myvalidator</literal>:
<programlisting>
ALTER FOREIGN DATA WRAPPER dbi VALIDATOR bob.myvalidator;
</programlisting></para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <command>ALTER FOREIGN DATA WRAPPER</command> conforms to ISO/IEC
   9075-9 (SQL/MED), except that the <literal>HANDLER</literal>,
   <literal>VALIDATOR</literal>, <literal>OWNER TO</literal>, and <literal>RENAME</literal>
   clauses are extensions.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createforeigndatawrapper"/></member>
   <member><xref linkend="sql-dropforeigndatawrapper"/></member>
  </simplelist>
 </refsect1>

</refentry>
