笔记二十八：自动补全与机遇上下文的提示
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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插叙请求到后端查询匹配项
- 对性能要求比较苛刻。ES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整个加载进内容，速度很快
- FST只能用于前缀查找
使用Completion Suggester 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
//定义mapping
PUT articles
{
"mappings": {
"properties": {
"title_completion": {
"type": "completion"
}
}
}
}
//写入数据
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":{}}
//查询
POST articles/_search?pretty
{
"size": 0,
"suggest": {
"article-suggest": {
"prefix": "e", //查询字段
"completion": {
"field": "title_completion"
}
}
}
}什么是Context Suggester
- Completion Suggester 的扩展
- 可以在搜索中加入耕读偶读上下文信息，例如，输入“star”
- 咖啡相关：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 - 地理信息位置
- 实现Context Suggester
- 定制一个Mapping
- 索引数据，并且为每个文档加入Conetxt信息
- 结合Context 进行Suggestion 查询
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":"movies"
// "comment_category":"coffee"
}
}
}
}
}精确度 和召回率
- 精准度
- Completion > Phrase > Term
- 召回率
- Term > Phrase > Completion
- 性能
- Completion > Phrase > Term
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