<code class="literal">$<em class="replaceable"><code>n</code></em></code>, and
   the call specifies data types and values for each such symbol.
   <em class="parameter"><code>read_only</code></em> and <em class="parameter"><code>count</code></em> have
   the same interpretation as in <code class="function">SPI_execute</code>.
  </p><p>
   The main advantage of this routine compared to
   <code class="function">SPI_execute</code> is that data values can be inserted
   into the command without tedious quotin