019.Elasticsearch搜索原理

# doc1
I really liked my small dogs, and I think my mom also liked them.
# doc2
He never liked any dogs, so I hope that my mom will not expect me to liked him

# 同义词转换
mom -> mother
small -> little
# 时态转换
liked -> like
# 类似：likes -> like
# 单复数转换
dogs -> dog
# 大小写转换
# 举例：Tom -> tom

doc1：hello you, and world is very good
doc2：hello, how are you

搜索请求：hello world
hello在doc1中出现1次，在doc2中出现1次
world在doc1中出现1次，在doc2中出现0次
所以doc1更相关

doc1：hello, today is very good
doc2：hi world, how are you
搜索请求：hello world
假设hello这个单词在全部文档中出现了10000次，world这个单词在全部文档中出现了100次
此时，doc1和doc2都是只能匹配一个单词，那么doc2的评分就比doc1靠前

doc1：{ "title": "hello article", "content": "yes"(一万个yes)}
doc2：{ "title": "my article", "content": "world yes"(一万个yes)}
搜索请求：hello world
doc1和doc2同样都是匹配到一个单词，且都出现了1次，但是doc1匹配到单词的field(title)比doc2匹配到单词的field(content)长度短
所有doc1评分更高

GET /test_index/test_type/_search?explain
{
  "query": {
    "match": {
      "test_field": "test hello"
    }
  }
}

doc1: {"name": "jack", "age": 27}
doc2: {"name": "tom", "age": 30}

PUT /my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "title": {
          "type": "text",
          "fielddata": true,
          "fields": {
            "raw": {
              "type": "keyword"
            }
          }
        }
      }
    }
  }
}

PUT /my_index/my_type/1
{
  "title": "first article"
}

PUT /my_index/my_type/2
{
  "title": "second article"
}

PUT /my_index/my_type/3
{
  "title": "third article"
}

# 使用分词的title进行排序
GET /my_index/my_type/_search
{
  "query": {
    "match_all": {}
  },
  "sort": [
    {
      "title": {
        "order": "desc"
      }
    }
  ]
}

{
  "took" : 25,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : null,
    "hits" : [
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "3",
        "_score" : null,
        "_source" : {
          "title" : "third article"
        },
        "sort" : [
          "third"
        ]
      },
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "2",
        "_score" : null,
        "_source" : {
          "title" : "second article"
        },
        "sort" : [
          "second"
        ]
      },
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "1",
        "_score" : null,
        "_source" : {
          "title" : "first article"
        },
        "sort" : [
          "first"
        ]
      }
    ]
  }
}

# 使用不分词的title进行排序
GET /my_index/my_type/_search
{
  "query": {
    "match_all": {}
  },
  "sort": [
    {
      "title.raw": {
        "order": "desc"
      }
    }
  ]
}

{
  "took" : 5,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : null,
    "hits" : [
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "3",
        "_score" : null,
        "_source" : {
          "title" : "third article"
        },
        "sort" : [
          "third article"
        ]
      },
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "2",
        "_score" : null,
        "_source" : {
          "title" : "second article"
        },
        "sort" : [
          "second article"
        ]
      },
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "1",
        "_score" : null,
        "_source" : {
          "title" : "first article"
        },
        "sort" : [
          "first article"
        ]
      }
    ]
  }
}