def _nextPage(self, offset):
        """Retrieves the next set of results from the service."""
        self.logger.debug("Iterator crecord=%s" % str(self.crecord))

        params = {
            'q': self.q,
            'rows': '0',
            'facet': 'true',
            'facet.field': self.field,
            'facet.limit': str(self.pagesize),
            'facet.offset': str(offset),
            'facet.zeros': 'false',
            'wt': 'python',
        }
        if self.fq is not None:
            params['fq'] = self.fq
        request = urllib.parse.urlencode(params, doseq=True)
        rsp = self.client.doPost(
            self.client.solrBase + '', request, self.client.formheaders
        )
        data = eval(rsp.read())
        try:
            self.res = data['facet_counts']['facet_fields'][self.field]
            self.logger.debug(self.res)
        except Exception:
            self.res = []
        self.index = 0