8、深度探秘搜索技术_基于boost的细粒度搜索条件权重控制

课程大纲
需求：搜索标题中包含java的帖子，同时呢，如果标题中包含hadoop或elasticsearch就优先搜索出来，同时呢，如果一个帖子包含java hadoop，一个帖子包含java elasticsearch，包含hadoop的帖子要比elasticsearch优先搜索出来
知识点，搜索条件的权重，boost，可以将某个搜索条件的权重加大，此时当匹配这个搜索条件和匹配另一个搜索条件的document，计算relevance score时，匹配权重更大的搜索条件的document，relevance score会更高，当然也就会优先被返回回来
默认情况下，搜索条件的权重都是一样的，都是1

GET /forum/_search 
{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "title": "blog"
          }
        }
      ],
      "should": [
        {
          "match": {
            "title": {
              "query": "java"
            }
          }
        },
        {
          "match": {
            "title": {
              "query": "hadoop"
            }
          }
        },
        {
          "match": {
            "title": {
              "query": "elasticsearch"
            }
          }
        },
        {
          "match": {
            "title": {
              "query": "spark",
              "boost": 5
            }
          }
        }
      ]
    }
  }
}

示例：

GET /forum/_search 
{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "title": "java"
          }
        }
      ],
      "should": [
        {
          "match": {
            "title": {
              "query": "hadoop",
              "boost": 6
            }
          }
        },
        {
          "match": {
            "title": {
              "query": "elasticsearch"
            }
          }
        },
        {
          "match": {
            "title": {
              "query": "flink",
              "boost": 5
            }
          }
        }
      ]
    }
  }
}



{
  "took" : 0,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 4,
      "relation" : "eq"
    },
    "max_score" : 6.547991,
    "hits" : [
      {
        "_index" : "forum",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 6.547991,
        "_source" : {
          "articleID" : "XHDK-A-1293-#fJ3",
          "userID" : 1,
          "hidden" : false,
          "postDate" : "2017-01-01",
          "tag" : [
            "java",
            "hadoop"
          ],
          "tag_cnt" : 2,
          "view_cnt" : 30,
          "title" : "this is java and hadoop blog"
        }
      },
      {
        "_index" : "forum",
        "_type" : "_doc",
        "_id" : "6",
        "_score" : 5.020876,
        "_source" : {
          "articleID" : "KDKE-B-9947-#kL1",
          "userID" : 3,
          "hidden" : false,
          "postDate" : "2018-01-02",
          "tag" : [
            "java",
            "flink"
          ],
          "tag_cnt" : 5,
          "view_cnt" : 50,
          "title" : "this is java, flink blog"
        }
      },
      {
        "_index" : "forum",
        "_type" : "_doc",
        "_id" : "4",
        "_score" : 2.1105356,
        "_source" : {
          "articleID" : "QQPX-R-3956-#aD8",
          "userID" : 2,
          "hidden" : true,
          "postDate" : "2017-01-02",
          "tag" : [
            "java",
            "elasticsearch"
          ],
          "tag_cnt" : 2,
          "view_cnt" : 40,
          "title" : "this is java and elasticsearch blog"
        }
      },
      {
        "_index" : "forum",
        "_type" : "_doc",
        "_id" : "2",
        "_score" : 1.0946829,
        "_source" : {
          "articleID" : "KDKE-B-9947-#kL5",
          "userID" : 1,
          "hidden" : false,
          "postDate" : "2017-01-02",
          "tag" : [
            "java"
          ],
          "tag_cnt" : 1,
          "view_cnt" : 50,
          "title" : "this is java blog"
        }
      }
    ]
  }
}