AS</literal> ... clause.  This function
   should be called by a PL trigger handler function after connecting.
  </para>
 </refsect1>

 <refsect1>
  <title>Arguments</title>

  <variablelist>
   <varlistentry>
    <term><literal>TriggerData *<parameter>tdata</parameter></literal></term>
    <listitem>
     <para>
       the <structname>TriggerData</structname> object passed to a trigger
       handler function as <literal>fcinfo->context</literal>
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

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

  <para>
   If the execution of the command was successful then the following
   (nonnegative) value will be returned:

   <variablelist>
    <varlistentry>
     <term><symbol>SPI_OK_TD_REGISTER</symbol></term>
     <listitem>
      <para>
       if the captured trigger data (if any) has been successfully registered
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

  <para>
   On error, one of the following negative values is returned:

   <variablelist>
    <varlistentry>
     <term><symbol>SPI_ERROR_ARGUMENT</symbol></term>
     <listitem>
      <para>
       if <parameter>tdata</parameter> is <symbol>NULL</symbol>
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>SPI_ERROR_UNCONNECTED</symbol></term>
     <listitem>
      <para>
       if called from an unconnected C function
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>SPI_ERROR_REL_DUPLICATE</symbol></term>
     <listitem>
      <para>
       if the name of any trigger data transient relation is already
       registered for this connection
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
</refentry>

<!-- *********************************************** -->

</sect1>

<sect1 id="spi-interface-support">
 <title>Interface Support Functions</title>

 <para>
  The functions described here provide an interface for extracting
  information from result sets returned by <function>SPI_execute</function> and
  other SPI functions.
 </para>

 <para>
  All functions described in this section can be used by both
  connected and unconnected C functions.
 </para>

<!-- *********************************************** -->

<refentry id="spi-spi-fname">
 <indexterm><primary>SPI_fname</primary></indexterm>

 <refmeta>
  <refentrytitle>SPI_fname</refentrytitle>
  <manvolnum>3</manvolnum>
 </refmeta>

 <refnamediv>
  <refname>SPI_fname</refname>
  <refpurpose>determine the column name for the specified column number</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
char * SPI_fname(TupleDesc <parameter>rowdesc</parameter>, int <parameter>colnumber</parameter>)
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <function>SPI_fname</function> returns a copy of the column name of the
   specified column.  (You can use <function>pfree</function> to
   release the copy of the name when you don't need it anymore.)
  </para>
 </refsect1>

 <refsect1>
  <title>Arguments</title>

  <variablelist>
   <varlistentry>
    <term><literal>TupleDesc <parameter>rowdesc</parameter></literal></term>
    <listitem>
     <para>
      input row description
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>int <parameter>colnumber</parameter></literal></term>
    <listitem>
     <para>
      column number (count starts at 1)
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

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

  <para>
   The column name; <symbol>NULL</symbol> if
   <parameter>colnumber</parameter> is out of range.
   <varname>SPI_result</varname> set to
   <symbol>SPI_ERROR_NOATTRIBUTE</symbol> on error.
  </para>
 </refsect1>
</refentry>

<!-- *********************************************** -->

<refentry id="spi-spi-fnumber">
 <indexterm><primary>SPI_fnumber</primary></indexterm>