ilt-in functions are checked locally after rows are
    fetched.  If such functions are available on the remote server and can be
    relied on to produce the same results as they do locally, performance can
    be improved by sending such <code class="literal">WHERE</code> clauses for remote
    execution.  This behavior can be controlled using the following option:
   </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">extensions</code> (<code class="type">s