ElasticSearch 单字符串多字段查询评分问题

1. 学习查询的api语法

   首先向es中titles写入两个文档

  

POST titles/_doc/1
{
  "title": "Quick brown rabbits",
  "body": "Brown rabbits are commonly seen."
}

POST titles/_doc/2
{
   "title": "Keeping pets healthy",
   "body": "My quick brown fox eats rabbits on a regular basis."
}

2 . 查询 tille 和body中 全文检索 quick brown的内容,语法如下

   1. 首先在写入文档的时候会先对写入的内容进行分词,分词后写入倒排索引,查询的时候也会对查询内容进行分词,分词后和倒排索引进行匹配，进行相关度查询

POST titles/_search
{
  "query": {
    "bool": {
      "should": [
        {"match": {"title": "quick brown"}},
        {"match": {"body": "quick brown"}}
      ]
    }
  }  
}

　结果如下 

{
  "took" : 2,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : 2.1213155,
    "hits" : [
      {
        "_index" : "titles",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 2.1213155,
        "_source" : {
          "title" : "Quick brown rabbits",
          "body" : "Brown rabbits are commonly seen."
        }
      },
      {
        "_index" : "titles",
        "_type" : "_doc",
        "_id" : "2",
        "_score" : 0.55788946,
        "_source" : {
          "title" : "Keeping pets healthy",
          "body" : "My quick brown fox eats rabbits on a regular basis."
        }
      }
    ]
  }
}

　　可以看到查询结果, 匹配到两个文档，文档1的评分比文档2的评分要高，直观感受应该是文档2的评分更匹配，这是因为should 查询评分是叠加的关系，会对body 和titile 中查询字段评分进行叠加  1，中body和title 中都有brown

      2 中的titile没有匹配，虽然body内容更加匹配。 有时候我们需要查询某个字段更加匹配展示给用户，可以使用dis_max 查询 

     

POST titles/_search
{
  "query": {
    "multi_match": {
      "query": "brown fox",
      "fields": ["title","body"],
      "type": "best_fields",
      "tie_breaker": 0.2
    }
  }
}

　　说明下 ，tile_breaker 是对除了最匹配的字段外,提升其他字段的权重得分.默认是0 也就是除了最匹配外，其他字段都忽略。 

   查询结果如下,可以看到文档2的评分比文档1高,查询也可以修改字段的权重，title^10 标识把title查询的权重提升10倍。 默认title和body的权重是一样的。 这个可以根据实际业务来看

  

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : 0.77041256,
    "hits" : [
      {
        "_index" : "titles",
        "_type" : "_doc",
        "_id" : "2",
        "_score" : 0.77041256,
        "_source" : {
          "title" : "Keeping pets healthy",
          "body" : "My quick brown fox eats rabbits on a regular basis."
        }
      },
      {
        "_index" : "titles",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 0.735369,
        "_source" : {
          "title" : "Quick brown rabbits",
          "body" : "Brown rabbits are commonly seen."
        }
      }
    ]
  }
}

　　

参考： Elasticsearch核心技术与实战