概述

继续跟中华石杉老师学习ES，第18篇

课程地址： https://www.roncoo.com/view/55

接上篇博客白话Elasticsearch17-match_phrase query 短语匹配搜索

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

slop 含义

官网中我们可以看到

A phrase query matches terms up to a configurable slop (which defaults to 0) in any order. Transposed terms have a slop of 2.

slop是什么呢？

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phrase match，就是proximity match，近似匹配
如果我们指定了slop，那么就允许搜索关键词进行移动，来尝试与doc进行匹配
搜索关键词k，可以有一定的距离，但是靠的越近，越先搜索出来，proximity match

例子

一个query string经过几次移动之后可以匹配到一个document，然后设置slop .

假设有个doc

hello world, java is very good, spark is also very good.

我们使用 match_phrase query 来搜索 java spark ，是肯定搜索不到的，因为 match_phrase query 会将java spark 作为一个整体来查找。

如果我们指定了slop，那么就允许java spark进行移动，来尝试与doc进行匹配

这里的slop，就是3，因为java spark这个短语，spark移动了3次，就可以跟一个doc匹配上了。

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，设置的是3，那么就ok

GET /forum/article/_search
{
    "query": {
        "match_phrase": {
            "title": {
                "query": "java spark",
                "slop":  3
            }
        }
    }
}

就可以把刚才那个doc匹配上，那个doc会作为结果返回

但是如果slop设置的是2，那么java spark，spark最多只能移动2次，此时跟doc是匹配不上的，那个doc是不会作为结果返回的。

示例一

我们那我们的测试数据来验证下

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

分析一下slop

data经过了3次移动才匹配到 spark data ,所以 slop设置为3即可，当然了设置成比3大的数字，肯定也是可以查询到的，这里的slop设置为3 ，可以理解为至少移动3次。

示例二

如果我们搜索data spark 呢？会不会匹配得到呢？答案是：可以

来分析一下

示例三

slop搜索下，关键词离的越近，relevance score就会越高 .

GET /forum/article/_search
{
  "query": {
    "match_phrase": {
      "title": {
        "query": "java blog",
        "slop": 5
      }
    }
  }
}

返回结果:

{
  "took": 2,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 3,
    "max_score": 0.81487787,
    "hits": [
      {
        "_index": "forum",
        "_type": "article",
        "_id": "2",
        "_score": 0.81487787,
        "_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": "1",
        "_score": 0.31424814,
        "_source": {
          "articleID": "XHDK-A-1293-#fJ3",
          "userID": 1,
          "hidden": false,
          "postDate": "2017-01-01",
          "tag": [
            "java",
            "hadoop"
          ],
          "tag_cnt": 2,
          "view_cnt": 30,
          "title": "this is java and elasticsearch blog",
          "content": "i like to write best elasticsearch article",
          "sub_title": "learning more courses",
          "author_first_name": "Peter",
          "author_last_name": "Smith",
          "new_author_last_name": "Smith",
          "new_author_first_name": "Peter"
        }
      },
      {
        "_index": "forum",
        "_type": "article",
        "_id": "4",
        "_score": 0.31424814,
        "_source": {
          "articleID": "QQPX-R-3956-#aD8",
          "userID": 2,
          "hidden": true,
          "postDate": "2017-01-02",
          "tag": [
            "java",
            "elasticsearch"
          ],
          "tag_cnt": 2,
          "view_cnt": 80,
          "title": "this is java, elasticsearch, hadoop blog",
          "content": "elasticsearch and hadoop are all very good solution, i am a beginner",
          "sub_title": "both of them are good",
          "author_first_name": "Robbin",
          "author_last_name": "Li",
          "new_author_last_name": "Li",
          "new_author_first_name": "Robbin"
        }
      }
    ]
  }
}