2014-09-15这个日期，但是看看下面的查询结果中的总数量：_all搜索全年就会返回所有推文，而使用字段date搜索年份却没有结果呢？为什么使用两者所得到的结果是不同的？_all和date在索引时没有被相同处理。我们来看看Elasticsearch是如何处理我们的文档结构的。我们可以对gb的tweet使用mapping请求：date字段被识别成了date类型。_all没有出现是因为他是默认字段，但是我们知道字段_all实际上是string类型的。date的字段和类型为string的字段的索引方式是不同的。date and fields of type string are indexed differently, and can thus be searched differently. That's not entirely surprising. You might expect that each of the core data types -- strings, numbers, booleans and dates -- might be indexed slightly differently. And this is true: there are slight differences.string fields) and fields that represent full text. This distinction is really important -- it's the thing that separates a search engine from all other databases.