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Elasticsearch短语或近似匹配及召回率案例深入剖析-搜索系统线上实战

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1 制作案例

POST /forum/article/_bulk
{ "update": { "_id": "1"} }
{ "doc" : {"author_first_name" : "Peter", "author_last_name" : "Smith"} }
{ "update": { "_id": "2"} }
{ "doc" : {"author_first_name" : "Smith", "author_last_name" : "Williams"} }
{ "update": { "_id": "3"} }
{ "doc" : {"author_first_name" : "Jack", "author_last_name" : "Ma"} }
{ "update": { "_id": "4"} }
{ "doc" : {"author_first_name" : "Robbin", "author_last_name" : "Li"} }
{ "update": { "_id": "5"} }
{ "doc" : {"author_first_name" : "Tonny", "author_last_name" : "Peter Smith"} }

//实现cross-fields搜索
PUT /forum/_mapping/article
{
  "properties": {
      "new_author_first_name": {
          "type":     "string",
          "copy_to":  "new_author_full_name" 
      },
      "new_author_last_name": {
          "type":     "string",
          "copy_to":  "new_author_full_name" 
      },
      "new_author_full_name": {
          "type":     "string"
      }
  }
}

//其实效果不佳
POST /forum/article/_bulk
{ "update": { "_id": "1"} }
{ "doc" : {"new_author_first_name" : "Peter", "new_author_last_name" : "Smith"} }		--> Peter Smith
{ "update": { "_id": "2"} }	
{ "doc" : {"new_author_first_name" : "Smith", "new_author_last_name" : "Williams"} }		--> Smith Williams
{ "update": { "_id": "3"} }
{ "doc" : {"new_author_first_name" : "Jack", "new_author_last_name" : "Ma"} }			--> Jack Ma
{ "update": { "_id": "4"} }
{ "doc" : {"new_author_first_name" : "Robbin", "new_author_last_name" : "Li"} }			--> Robbin Li
{ "update": { "_id": "5"} }
{ "doc" : {"new_author_first_name" : "Tonny", "new_author_last_name" : "Peter Smith"} }		--> Tonny Peter Smith

GET /forum/article/_search
{
  "query": {
    "match": {
      "new_author_full_name":       "Peter Smith"
    }
  }
}

//测试短语匹配
POST /forum/article/5/_update
{
  "doc": {
    "content": "spark is best big data solution based on scala ,an programming language similar to java spark"
  }
}

//单单包含java的doc也返回了，不是我们想要的结果
GET /forum/article/_search
{
  "query": {
    "match": {
      "content": "java spark"
    }
  }
}
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2 短语匹配(match_phrase)

要求：只有包含java spark这个短语的doc才返回了，只包含java的doc不会返回

GET /forum/article/_search
{
    "query": {
        "match_phrase": {
            "content": "java spark"
        }
    }
}
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term position的意思

hello world, java spark		doc1
hi, spark java			doc2

hello 		doc1(0)		
wolrd		doc1(1)
java		doc1(2) doc2(2)
spark		doc1(3) doc2(1)

了解什么是分词后的position

GET _analyze
{
  "text": "hello world, java spark",
  "analyzer": "standard"
}
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3 近似匹配(slop)

query string，搜索文本中的几个term，要经过几次移动才能与一个document匹配，这个移动的次数，就是slop
slop的含义，不仅仅是说一个query string terms移动几次，跟一个doc匹配上。一个query string terms，最多可以移动几次去尝试跟一个doc匹配上
slop搜索下，关键词离的越近，relevance score就会越高，

GET /forum/article/_search
{
  "query": {
    "match_phrase": {
      "content": {
        "query": "spark data",
        "slop": 3
      }
    }
  }
}

spark is best big data solution based on scala ,an programming language similar to java spark

spark data
	  --> data
	      --> data
spark		  --> data

GET /forum/article/_search
{
  "query": {
    "match_phrase": {
      "content": {
        "query": "java best",
        "slop": 15
      }
    }
  }
}

{
  "took": 3,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 2,
    "max_score": 0.65380025,
    "hits": [
      {
        "_index": "forum",
        "_type": "article",
        "_id": "2",
        "_score": 0.65380025,
        "_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",
          "content": "i think java is the best programming language",
          "sub_title": "learned a lot of course",
          "author_first_name": "Smith",
          "author_last_name": "Williams",
          "new_author_last_name": "Williams",
          "new_author_first_name": "Smith"
        }
      },
      {
        "_index": "forum",
        "_type": "article",
        "_id": "5",
        "_score": 0.07111243,
        "_source": {
          "articleID": "DHJK-B-1395-#Ky5",
          "userID": 3,
          "hidden": false,
          "postDate": "2017-03-01",
          "tag": [
            "elasticsearch"
          ],
          "tag_cnt": 1,
          "view_cnt": 10,
          "title": "this is spark blog",
          "content": "spark is best big data solution based on scala ,an programming language similar to java spark",
          "sub_title": "haha, hello world",
          "author_first_name": "Tonny",
          "author_last_name": "Peter Smith",
          "new_author_last_name": "Peter Smith",
          "new_author_first_name": "Tonny"
        }
      }
    ]
  }
}
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4 优先满足召回率

优先满足召回率，意思是：java spark，包含java的也返回，包含spark的也返回，包含java和spark的也返回；同时兼顾精准度，就是包含java和spark，同时java和spark离的越近的doc排在最前面

GET /forum/article/_search 
{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "content": "java spark"
          }
        }
      ],
      "should": [
        {
          "match_phrase": {
            "content": {
              "query": "java spark",
              "slop": 50
            }
          }
        }
      ]
    }
  }
}

{
  "took": 5,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 2,
    "max_score": 1.258609,
    "hits": [
      {
        "_index": "forum",
        "_type": "article",
        "_id": "5",
        "_score": 1.258609,
        "_source": {
          "articleID": "DHJK-B-1395-#Ky5",
          "userID": 3,
          "hidden": false,
          "postDate": "2017-03-01",
          "tag": [
            "elasticsearch"
          ],
          "tag_cnt": 1,
          "view_cnt": 10,
          "title": "this is spark blog",
          "content": "spark is best big data solution based on scala ,an programming language similar to java spark",
          "sub_title": "haha, hello world",
          "author_first_name": "Tonny",
          "author_last_name": "Peter Smith",
          "new_author_last_name": "Peter Smith",
          "new_author_first_name": "Tonny",
          "followers": [
            "Jack",
            "Robbin Li"
          ]
        }
      },
      {
        "_index": "forum",
        "_type": "article",
        "_id": "2",
        "_score": 0.68640786,
        "_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",
          "content": "i think java is the best programming language",
          "sub_title": "learned a lot of course",
          "author_first_name": "Smith",
          "author_last_name": "Williams",
          "new_author_last_name": "Williams",
          "new_author_first_name": "Smith",
          "followers": [
            "Tom",
            "Jack"
          ]
        }
      }
    ]
  }
}
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