在/terms查询的solr中，我得到文档频率df降序的条款。
但是，我希望按升序排列条款，即首先列出文档频率最低的字词。
solr wiki有一个排序字段terms.sort没有asc，desc orderc
Defines how to sort the terms returned. Valid options are count,
which sorts by the term frequency, with the highest term frequency
first, or index, which sorts in index order.
Example: terms.sort=index