<term><literal>TD["new"]</literal></term>
     <term><literal>TD["old"]</literal></term>
     <listitem>
      <para>
       For a row-level trigger, one or both of these fields contain
       the respective trigger rows, depending on the trigger event.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TD["name"]</literal></term>
     <listitem>
      <para>
       contains the trigger name.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TD["table_name"]</literal></term>
     <listitem>
      <para>
       contains the name of the table on which the trigger occurred.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TD["table_schema"]</literal></term>
     <listitem>
      <para>
       contains the schema of the table on which the trigger occurred.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TD["relid"]</literal></term>
     <listitem>
      <para>
       contains the OID of the table on which the trigger occurred.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TD["args"]</literal></term>
     <listitem>
      <para>
       If the <command>CREATE TRIGGER</command> command
       included arguments, they are available in <literal>TD["args"][0]</literal> to
       <literal>TD["args"][<replaceable>n</replaceable>-1]</literal>.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

  <para>
   If <literal>TD["when"]</literal> is <literal>BEFORE</literal> or
   <literal>INSTEAD OF</literal> and
   <literal>TD["level"]</literal> is <literal>ROW</literal>, you can
   return <literal>None</literal> or <literal>"OK"</literal> from the
   Python function to indicate the row is unmodified,
   <literal>"SKIP"</literal> to abort the event, or if <literal>TD["event"]</literal>
   is <command>INSERT</command> or <command>UPDATE</command> you can return
   <literal>"MODIFY"</literal> to indicate you've modified the new row.
   Otherwise the return value is ignored.
  </para>
 </sect1>

 <sect1 id="plpython-database">
  <title>Database Access</title>

  <para>
   The PL/Python language module automatically imports a Python module
   called <literal>plpy</literal>.  The functions and constants in
   this module are available to you in the Python code as
   <literal>plpy.<replaceable>foo</replaceable></literal>.
  </para>

  <sect2 id="plpython-database-access-funcs">
    <title>Database Access Functions</title>

  <para>
   The <literal>plpy</literal> module provides several functions to execute
   database commands:
  </para>

  <variablelist>
   <varlistentry>
    <term><literal>plpy.<function>execute</function>(<replaceable>query</replaceable> [, <replaceable>limit</replaceable>])</literal></term>
    <listitem>
     <para>
      Calling <function>plpy.execute</function> with a query string and an
      optional row limit argument causes that query to be run and the result to
      be returned in a result object.
     </para>

     <para>
      If <replaceable>limit</replaceable> is specified and is greater than
      zero, then <function>plpy.execute</function> retrieves at
      most <replaceable>limit</replaceable> rows, much as if the query
      included a <literal>LIMIT</literal>
      clause.  Omitting <replaceable>limit</replaceable> or specifying it as
      zero results in no row limit.
     </para>

     <para>
      The result object emulates a list or dictionary object.  The result
      object can be accessed by row number and column name.  For example:
<programlisting>
rv = plpy.execute("SELECT * FROM my_table", 5)
</programlisting>
      returns up to 5 rows from <literal>my_table</literal>.  If
      <literal>my_table</literal> has a column
      <literal>my_column</literal>, it would be accessed as:
<programlisting>
foo = rv[i]["my_column"]
</programlisting>
      The number of rows returned