<refname>dblink_build_sql_update</refname>
   <refpurpose>builds an UPDATE statement using a local tuple, replacing
    the primary key field values with alternative supplied values
   </refpurpose>
  </refnamediv>

  <refsynopsisdiv>
<synopsis>
dblink_build_sql_update(text relname,
                        int2vector primary_key_attnums,
                        integer num_primary_key_atts,
                        text[] src_pk_att_vals_array,
                        text[] tgt_pk_att_vals_array) returns text
</synopsis>
  </refsynopsisdiv>

  <refsect1>
   <title>Description</title>

   <para>
    <function>dblink_build_sql_update</function> can be useful in doing selective
    replication of a local table to a remote database.  It selects a row
    from the local table based on primary key, and then builds an SQL
    <command>UPDATE</command> command that will duplicate that row, but with
    the primary key values replaced by the values in the last argument.
    (To make an exact copy of the row, just specify the same values for
    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,