 ready to receive the next SQL
       command.  The return value is 0  on  successful  completion,
       nonzero otherwise.  (Use <a class="xref" href="libpq-status.html#LIBPQ-PQERRORMESSAGE"><code class="function">PQerrorMessage</code></a> to
       retrieve details if the return value is nonzero.)
      </p><p>
       When using <a class="xref" href="libpq-async.html#LIBPQ-PQGETRESULT"><code class="function">PQgetResult</code></a>, the application should
       respond to a <code class="literal">PGRES_CO