4.12-自动补全与基于上下文的提示

The Completion Suggester

• Completion Suggester 提供了“⾃动完成” (Auto Complete) 的功能。⽤户每输⼊⼀个 字符，就需要即时发送⼀个查询请求到后段查找匹配项

• 对性能要求⽐较苛刻。Elasticsearch 采⽤了不同的数据结构，并⾮通过倒排索引来完成。
  ⽽是将 Analyze 的数据编码成 FST 和索引⼀起存放。FST 会被 ES 整个加载进内存， 速度很快

• FST 只能⽤于前缀查找

使⽤ Completion Suggester 的⼀些步骤

• 定义 Mapping，使⽤ “completion” type

• 索引数据

• 运⾏ “suggest” 查询，得到搜索建议

PUT articles
{
  "mappings": {
    "properties": {
      "title_completion":{
        "type": "completion"
      }
    }
  }
}

索引数据

POST articles/_bulk
{ "index" : { } }
{ "title_completion": "lucene is very cool"}
{ "index" : { } }
{ "title_completion": "Elasticsearch builds on top of lucene"}
{ "index" : { } }
{ "title_completion": "Elasticsearch rocks"}
{ "index" : { } }
{ "title_completion": "elastic is the company behind ELK stack"}
{ "index" : { } }
{ "title_completion": "Elk stack rocks"}
{ "index" : {} }

搜索数据

POST articles/_search?pretty
{
  "size": 0,
  "suggest": {
    "article-suggester": {
      "prefix": "elk ",
      "completion": {
        "field": "title_completion"
      }
    }
  }
}

res

什么是 Context Suggester

• Completion Suggester 的扩展

• 可以在搜索中加⼊更多的上下⽂信息，例如，输⼊ “star”

  • 咖啡相关：建议 “Starbucks”

  • 电影相关：”star wars”

实现 Context Suggester

• 可以定义两种类型的 Context

  • Category – 任意的字符串

  • Geo – 地理位置信息

• 实现 Context Suggester 的具体步骤

  • 定制⼀个 Mapping

  • 索引数据，并且为每个⽂档加⼊ Context 信息

  • 结合 Context 进⾏ Suggestion 查询

定义 Mapping

• 增加 Contexts

  • Type

  • name

PUT comments/_mapping
{
  "properties": {
    "comment_autocomplete":{
      "type": "completion",
      "contexts":[{
        "type":"category",
        "name":"comment_category"
      }]
    }
  }
}

索引数据

image.png

不同的上下⽂，⾃动提示

POST comments/_search
{
  "suggest": {
    "MY_SUGGESTION": {
      "prefix": "sta",
      "completion":{
        "field":"comment_autocomplete",
        "contexts":{
          "comment_category":"coffee"
        }
      }
    }
  }
}

image.png

精准度和召回率

• 精准度

  • Completion > Phrase > Term

• 召回率

  • Term > Phrase > Completion

• 性能

  • Completion > Phrase > Term

本节知识点回顾

• Completion Suggester，对性能要求⽐较苛刻。采⽤了不同的数据结构，并⾮通过倒排
  索引来完成。⽽是将 Analyze 的数据编码成 FST 和索引⼀起存放。FST 会被 ES 整个 加载进内存，速度很快

• 需要设置特定的 Mapping

• Context Completion Suggester ⽀持结合不同的上下⽂，给出推荐

课程demo

DELETE articles
PUT articles
{
  "mappings": {
    "properties": {
      "title_completion":{
        "type": "completion"
      }
    }
  }
}

POST articles/_bulk
{ "index" : { } }
{ "title_completion": "lucene is very cool"}
{ "index" : { } }
{ "title_completion": "Elasticsearch builds on top of lucene"}
{ "index" : { } }
{ "title_completion": "Elasticsearch rocks"}
{ "index" : { } }
{ "title_completion": "elastic is the company behind ELK stack"}
{ "index" : { } }
{ "title_completion": "Elk stack rocks"}
{ "index" : {} }


POST articles/_search?pretty
{
  "size": 0,
  "suggest": {
    "article-suggester": {
      "prefix": "elk ",
      "completion": {
        "field": "title_completion"
      }
    }
  }
}


DELETE comments
PUT comments
PUT comments/_mapping
{
  "properties": {
    "comment_autocomplete":{
      "type": "completion",
      "contexts":[{
        "type":"category",
        "name":"comment_category"
      }]
    }
  }
}

POST comments/_doc
{
  "comment":"I love the star war movies",
  "comment_autocomplete":{
    "input":["star wars"],
    "contexts":{
      "comment_category":"movies"
    }
  }
}

POST comments/_doc
{
  "comment":"Where can I find a Starbucks",
  "comment_autocomplete":{
    "input":["starbucks"],
    "contexts":{
      "comment_category":"coffee"
    }
  }
}


POST comments/_search
{
  "suggest": {
    "MY_SUGGESTION": {
      "prefix": "sta",
      "completion":{
        "field":"comment_autocomplete",
        "contexts":{
          "comment_category":"coffee"
        }
      }
    }
  }
}