白话Elasticsearch17-深度探秘搜索技术之match_phrase query 短语匹配搜索

网友投稿 738 2022-05-29

文章目录

概述

官网

近似匹配

例子

match query

match phrase query

term position

match_phrase的基本原理

概述

继续跟中华石杉老师学习ES,第17篇

课程地址: https://www.roncoo.com/view/55

官网

https://www.elastic.co/guide/en/elasticsearch/reference/current/full-text-queries.html

https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-match-query-phrase.html

近似匹配

假设content字段中有2个语句

java is my favourite programming language, and I also think spark is a very good big data system. java spark are very related, because scala is spark's programming language and scala is also based on jvm like java.

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使用match query , 搜索java spark ,DSL 大致如下

{ "match": { "content": "java spark" } }

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content 被拆分为两个单词 java 和 spark去匹配,所以如上两个doc都能被查询出来。

match query,只能搜索到包含java和spark的document,但是不知道java和spark是不是离的很近. 包含java或包含spark,或包含java和spark的doc,都会被查询出来。我们其实并不知道哪个doc,java和spark距离的比较近。

如果我们希望搜索java spark,中间不能插入任何其他的字符, 这个时候match就无能为力了 。

再比如 , 如果我们要尽量让java和spark离的很近的document优先返回,要给它一个更高的relevance score,这就涉及到了proximity match,近似匹配.

例子

假设要实现两个需求:

java spark,就靠在一起,中间不能插入任何其他字符,就要搜索出来这种doc

java spark,但是要求,java和spark两个单词靠的越近,doc的分数越高,排名越靠前

要实现上述两个需求,用match做全文检索,是搞不定的,必须得用proximity match,近似匹配

phrase match:短语匹配

proximity match:近似匹配

这里我们要学习的是phrase match,就是仅仅搜索出java和spark靠在一起的那些doc,比如有个doc,是java use’d spark,不行。必须是比如java spark are very good friends,是可以搜索出来的。

match phrase query,就是要去将多个term作为一个短语,一起去搜索,只有包含这个短语的doc才会作为结果返回。

不像是match query,java spark,java的doc也会返回,spark的doc也会返回。

match query

为了做比对,我们先看下match query的查询结果

GET /forum/article/_search { "query": { "match": { "content": "java spark" } } }

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返回结果

{ "took": 40, "timed_out": false, "_shards": { "total": 1, "successful": 1, "skipped": 0, "failed": 0 }, "hits": { "total": 2, "max_score": 1.8166281, "hits": [ { "_index": "forum", "_type": "article", "_id": "5", "_score": 1.8166281, "_source": { "articleID": "DHJK-B-1395-#Ky5", "userID": 3, "hidden": false, "postDate": "2019-05-01", "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" } }, { "_index": "forum", "_type": "article", "_id": "2", "_score": 0.7721133, "_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" } } ] } }

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可以看到单单包含java的doc也返回了,不是我们想要的结果 。

match phrase query

为了演示match phrase query的功能,我们先调整一下测试数据

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

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将id=5的doc的content设置为恰巧包含java spark这个短语 。

GET /forum/article/_search { "query": { "match_phrase": { "content": "java spark" } } }

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返回结果

{ "took": 47, "timed_out": false, "_shards": { "total": 1, "successful": 1, "skipped": 0, "failed": 0 }, "hits": { "total": 1, "max_score": 1.4302213, "hits": [ { "_index": "forum", "_type": "article", "_id": "5", "_score": 1.4302213, "_source": { "articleID": "DHJK-B-1395-#Ky5", "userID": 3, "hidden": false, "postDate": "2019-05-01", "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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从结果中可以看到只有包含java spark这个短语的doc才返回,只包含java的doc不会返回

term position

分词后,每个单词就是一个term

分词后 , es还记录了 每个field的位置。

举个例子 两个doc 如下:

hello world, java spark doc1

hi, spark java doc2

建立倒排索引后

可以通过如下API来看下

GET _analyze { "text": "hello world, java spark", "analyzer": "standard" }

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返回:

{ "tokens": [ { "token": "hello", "start_offset": 0, "end_offset": 5, "type": "", "position": 0 }, { "token": "world", "start_offset": 6, "end_offset": 11, "type": "", "position": 1 }, { "token": "java", "start_offset": 13, "end_offset": 17, "type": "", "position": 2 }, { "token": "spark", "start_offset": 18, "end_offset": 23, "type": "", "position": 3 } ] }

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白话Elasticsearch17-深度探秘搜索技术之match_phrase query 短语匹配搜索

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通过position 可以看到位置信息 。

match_phrase的基本原理

理解下索引中的position,match_phrase

两个doc 如下

hello world, java spark doc1 hi, spark java doc2

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java spark , 采用match phrase来查询

首先 java spark 被拆成 java和spark ,分别取索引中查找

java 出现在 doc1(2) doc2(2) spark 出现在 doc1(3) doc2(1)

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要找到每个term都在的一个共有的那些doc,就是要求一个doc,必须包含每个term,才能拿出来继续计算

doc1 --> java和spark --> spark position恰巧比java大1 --> java的position是2,spark的position是3,恰好满足条件

doc1符合条件

doc2 --> java和spark --> java position是2,spark position是1,spark position比java position小1,而不是大1 --> 光是position就不满足,那么doc2不匹配 .

Elasticsearch Java 实时流计算服务 CS

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