ES底层分数计算逻辑

relevance score算法，简单来说，就是计算出，一个索引中的文本，与搜索文本，他们之间的关联匹配程度。Elasticsearch使用的是 term frequency/inverse document frequency算法，简称为TF/IDF算法

Term frequency：搜索文本中的各个词条在field文本中出现了多少次，出现次数越多，就越相关

PUT /score/_doc/1
{\"doc\":\"hello you, and world is very good\"}
PUT /score/_doc/2
{\"doc\":\"hello, how are you\"}GET /score/_search
{