     <code class="function">SPI_execute_with_args</code> assumes that no parameters
      are null.  Otherwise, each entry of the <em class="parameter"><code>nulls</code></em>
      array should be <code class="literal">' '</code> if the corresponding parameter
      value is non-null, or <code class="literal">'n'</code> if the corresponding parameter
      value is null.  (In the latter case, the actual value in the
      corresponding <em class="parameter"><code>values</code></em> entry doesn't matter.) 