the last two arguments.)  The <command>UPDATE</command> command always assigns
    all fields of the row &mdash; the main difference between this and
    <function>dblink_build_sql_insert</function> is that it's assumed that
    the target row already exists in the remote table.
   </para>
  </refsect1>

  <refsect1>
   <title>Arguments</title>

   <variablelist>
    <varlistentry>
     <term><parameter>relname</parameter></term>
     <listitem>
      <para>
       Name of a local relation, for example <literal>foo</literal> or
       <literal>myschema.mytab</literal>.  Include double quotes if the
       name is mixed-case or contains special characters, for
       example <literal>"FooBar"</literal>; without quotes, the string
       will be folded to lower case.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><parameter>primary_key_attnums</parameter></term>
     <listitem>
      <para>
       Attribute numbers (1-based) of the primary key fields,
       for example <literal>1 2</literal>.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><parameter>num_primary_key_atts</parameter></term>
     <listitem>
      <para>
       The number of primary key fields.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><parameter>src_pk_att_vals_array</parameter></term>
     <listitem>
      <para>
       Values of the primary key fields to be used to look up the
       local tuple.  Each field is represented in text form.
       An error is thrown if there is no local row with these
       primary key values.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><parameter>tgt_pk_att_vals_array</parameter></term>
     <listitem>
      <para>
       Values of the primary key fields to be placed in the resulting
       <command>UPDATE</command> command.  Each field is represented in text form.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </refsect1>

  <refsect1>
   <title>Return Value</title>

   <para>Returns the requested SQL statement as text.</para>
  </refsect1>

  <refsect1>
   <title>Notes</title>

   <para>
    As of <productname>PostgreSQL</productname> 9.0, the attribute numbers in
    <parameter>primary_key_attnums</parameter> are interpreted as logical
    column numbers, corresponding to the column's position in
    <literal>SELECT * FROM relname</literal>.  Previous versions interpreted the
    numbers as physical column positions.  There is a difference if any
    column(s) to the left of the indicated column have been dropped during
    the lifetime of the table.
   </para>
  </refsect1>

  <refsect1>
   <title>Examples</title>

<screen>
SELECT dblink_build_sql_update('foo', '1 2', 2, '{"1", "a"}', '{"1", "b"}');
                   dblink_build_sql_update
-------------------------------------------------------------
 UPDATE foo SET f1='1',f2='b',f3='1' WHERE f1='1' AND f2='b'
(1 row)
</screen>
  </refsect1>
 </refentry>

</sect1>