LIBPQ-PQERRORMESSAGE"><code class="function">PQerrorMessage</code></a> for the reason).
      </p><p>
       When <em class="parameter"><code>async</code></em> is true (not zero),
       <a class="xref" href="libpq-copy.html#LIBPQ-PQGETCOPYDATA"><code class="function">PQgetCopyData</code></a> will not block waiting for input; it
       will return zero if the <code class="command">COPY</code> is still in progress
       but no complete row is available.  (In this case wait for read-ready
       and then cal