13.1.5 Keyword Analyzer 关键字解析器

关键字类型的解析器会将整个分词当作一个不可再分割的对象来处理。这在处理类似邮政编码，id号等数据的时候会非常有用。但要注意的是，使用关键字解析器来处理不如直接把字段标记为not_analyzed来得更直观。

An analyzer of type keyword that "tokenizes" an entire stream as a single token. This is useful for data like zip codes, ids and so on. Note, when using mapping definitions, it might make more sense to simply mark the field as not_analyzed.