ElasticSearch教程——Search相关、deep paging问题及解决方案

柔情只为你懂 2021-09-27 13:12 214阅读 0赞

**ElasticSearch汇总请查看：[ElasticSearch教程——汇总篇][ElasticSearch]**

# 搜索所有索引 #

GET /_search

## 返回结果 ##

{
      "took": 6,
      "timed_out": false,
      "_shards": {
        "total": 16,
        "successful": 16,
        "skipped": 0,
        "failed": 0
      },
      "hits": {
        "total": 8,
        "max_score": 1,
        "hits": [
          {
            "_index": ".kibana",
            "_type": "doc",
            "_id": "config:6.4.0",
            "_score": 1,
            "_source": {
              "type": "config",
              "updated_at": "2018-09-18T09:30:18.949Z",
              "config": {
                "buildNum": 17929,
                "telemetry:optIn": true
              }
            }
          },
          {
            "_index": "blog",
            "_type": "article",
            "_id": "eTmX5mUBtZGWutGW0TNs",
            "_score": 1,
            "_source": {
              "title": "New version of Elasticsearch released!",
              "content": "Version 1.0 released today!",
              "priority": 10,
              "tags": [
                "announce",
                "elasticsearch",
                "release"
              ]
            }
          },
          {
            "_index": "ecommerce",
            "_type": "product",
            "_id": "2",
            "_score": 1,
            "_source": {
              "name": "jiajieshi yagao",
              "desc": "youxiao fangzhu",
              "price": 25,
              "producer": "jiajieshi producer",
              "tags": [
                "fangzhu"
              ]
            }
          },
          {
            "_index": "ecommerce",
            "_type": "product",
            "_id": "J3fLFWYBBoLynJN1-kOG",
            "_score": 1,
            "_source": {
              "name": "test yagao",
              "desc": "youxiao fangzhu"
            }
          },
          {
            "_index": "blog",
            "_type": "article",
            "_id": "1",
            "_score": 1,
            "_source": {
              "id": "1",
              "title": "New version of Elasticsearch released!",
              "content": "Version 1.0 released today!",
              "priority": 10,
              "tags": [
                "announce",
                "elasticsearch",
                "release"
              ]
            }
          },
          {
            "_index": "ecommerce",
            "_type": "product",
            "_id": "KXfSFWYBBoLynJN1TUPo",
            "_score": 1,
            "_source": {
              "name": "test yagao2",
              "desc": "youxiao fangzhu2"
            }
          },
          {
            "_index": "index",
            "_type": "fulltext",
            "_id": "1",
            "_score": 1,
            "_source": {
              "content": "中国驻洛杉矶领事馆遭亚裔男子枪击 嫌犯已自首"
            }
          },
          {
            "_index": "ecommerce",
            "_type": "product",
            "_id": "3",
            "_score": 1,
            "_source": {
              "name": "zhonghua yagao",
              "desc": "caoben zhiwu",
              "price": 40,
              "producer": "zhonghua producer",
              "tags": [
                "qingxin"
              ]
            }
          }
        ]
      }
    }

## 返回参数含义 ##

took：整个搜索请求花费了多少毫秒
    
    hits.total：本次搜索，返回了几条结果
    hits.max_score：本次搜索的所有结果中，最大的相关度分数是多少，每一条document对于search的相关度，越相关，_score分数越大，排位越靠前
    hits.hits：默认查询前10条数据，完整数据，_score降序排序
    
    shards：shards fail的条件（primary和replica全部挂掉），不影响其他shard。默认情况下来说，一个搜索请求，会打到一个index的所有primary shard上去，当然了，每个primary shard都可能会有一个或多个replic shard，所以请求也可以到primary shard的其中一个replica shard上去。
    
    timeout：默认无timeout，当搜索得特别深，需要花费很长时间的时候我们可以设置timeout，当时间达到这个timeout的时候就返回当前的搜索结果（不继续搜索下去了）
    
    timeout=10ms，timeout=1s，timeout=1m
    GET /_search?timeout=10m

# 查询指定index #

GET /blog/_search

# 查询多个指定index #

GET /.kibana,blog/_search

# 按照通配符去匹配多个索引 #

GET /*log/_search

## 返回结果 ##

{
      "took": 6,
      "timed_out": false,
      "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
      },
      "hits": {
        "total": 2,
        "max_score": 1,
        "hits": [
          {
            "_index": "blog",
            "_type": "article",
            "_id": "eTmX5mUBtZGWutGW0TNs",
            "_score": 1,
            "_source": {
              "title": "New version of Elasticsearch released!",
              "content": "Version 1.0 released today!",
              "priority": 10,
              "tags": [
                "announce",
                "elasticsearch",
                "release"
              ]
            }
          },
          {
            "_index": "blog",
            "_type": "article",
            "_id": "1",
            "_score": 1,
            "_source": {
              "id": "1",
              "title": "New version of Elasticsearch released!",
              "content": "Version 1.0 released today!",
              "priority": 10,
              "tags": [
                "announce",
                "elasticsearch",
                "release"
              ]
            }
          }
        ]
      }
    }

# 搜索一个index下指定的type的数据 #

GET /index1/type1/_search

# 搜索一个index下多个type的数据 #

由于在6.0之后每个index下最多只能有一个type，故在该版本及其以后无意义

GET /index1/type1,type2/_search

# 搜索多个index下的多个type的数据 #

由于在6.0之后每个index下最多只能有一个type，故在该版本及其以后无意义

GET /index1,index2/type1,type2/_search

# 搜索所有index下的指定type的数据 #

由于在6.0之后每个index下最多只能有一个type，故在该版本及其以后无意义

GET /_all/type1,type2/_search

# 分页搜索 #

添加"?from=0&size=2"

注：当数据量达到50000条以上时，用下面的scroll滚动的方式进行代替

GET /_search?from=0&size=2

返回结果

{
      "took": 3,
      "timed_out": false,
      "_shards": {
        "total": 16,
        "successful": 16,
        "skipped": 0,
        "failed": 0
      },
      "hits": {
        "total": 8,
        "max_score": 1,
        "hits": [
          {
            "_index": ".kibana",
            "_type": "doc",
            "_id": "config:6.4.0",
            "_score": 1,
            "_source": {
              "type": "config",
              "updated_at": "2018-09-18T09:30:18.949Z",
              "config": {
                "buildNum": 17929,
                "telemetry:optIn": true
              }
            }
          },
          {
            "_index": "blog",
            "_type": "article",
            "_id": "eTmX5mUBtZGWutGW0TNs",
            "_score": 1,
            "_source": {
              "title": "New version of Elasticsearch released!",
              "content": "Version 1.0 released today!",
              "priority": 10,
              "tags": [
                "announce",
                "elasticsearch",
                "release"
              ]
            }
          }
        ]
      }
    }

# deep paging问题 #

deep paging简单来说，就是搜索的特别深，比如总共有60000条数据，现在有3个primary shard，每个shard上分20000条，每页是10条数据，这个时候你要搜索到第1000页，实际上要拿到的是10001-10010，该怎么拿呢？  
请求首先可能是打到一个不包含这个index的shard的node上，这个node就是一个coordinate node，这个coordinate node就会将搜索请求转发到index的三个shard所在的node上去。

要搜索60000条数据中的第1000页，实际上每个shard都要将内部的20000条数据中的第1-10010条数据拿出来，不是10条，是10010条数据，3个shard每个shard都返回10010条数据给coordinate node，coordinate node会收到总共30030条数据，然后排序取到所需的那10条数据，其实就是我们要的最后的第1000页的10条数据。

举个例子，现在有60个带编号的球（从1到60），我现在随机给他们放到三个篮子里面（他们在篮子里面已经排好序了），现在我要取出第10-12个球，那我是不是应该先把各个篮子里面前12个球取出来放到一起（篮子里面的球是随机放的，无规律），共计36个球，然后汇总进行排序后，在这个结果中取出第10-12个球！！！

## 缺点 ##

搜索过深的时候就需要在coordinate node上保存大量的数据，还要进行大量数据的排序，排序之后再取出对应的那一页，所以这个过程，既消耗网络宽带，耗费内存，还消耗cpu。这就是deep paging的性能问题，我们应该尽量避免出现这种deep paging操作。

## 解决方案 ##

为了解决上面的问题，elasticsearch提出了一个scroll滚动的方式，这个滚动的方式原理就是通过每次查询后，返回一个scroll\_id。根据这个scroll\_id 进行下一页的查询。可以把这个scroll\_id理解为通常关系型数据库中的游标。但是，这种scroll方式的缺点是不能够进行反复查询，也就是说，只能进行下一页，不能进行上一页。

经过分析，如果数据达到了50000条以上，那么用户基本上是不会考虑每条都去看的，用户需要的是最后对数据分析处理后的结果。而如果小于50000条的时候我们可以使用from size的方式进行分页的查询。那么这种方式存在是为了什么情景呢。应该是为了分批次的检索所有数据。

### 实现步骤 ###

1.首先取出前2条，并且得到scroll\_id（这里的3s代表的是持续滚动时间，如果过了3秒钟，还没有查询下一页，那么这个scroll\_id就会失效）。

GET /_search?scroll=3s&size=2

返回结果

{
      "_scroll_id": "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",
      "took": 10,
      "timed_out": false,
      "_shards": {
        "total": 16,
        "successful": 16,
        "skipped": 0,
        "failed": 0
      },
      "hits": {
        "total": 8,
        "max_score": 1,
        "hits": [
          {
            "_index": ".kibana",
            "_type": "doc",
            "_id": "config:6.4.0",
            "_score": 1,
            "_source": {
              "type": "config",
              "updated_at": "2018-09-18T09:30:18.949Z",
              "config": {
                "buildNum": 17929,
                "telemetry:optIn": true
              }
            }
          },
          {
            "_index": "blog",
            "_type": "article",
            "_id": "eTmX5mUBtZGWutGW0TNs",
            "_score": 1,
            "_source": {
              "title": "New version of Elasticsearch released!",
              "content": "Version 1.0 released today!",
              "priority": 10,
              "tags": [
                "announce",
                "elasticsearch",
                "release"
              ]
            }
          }
        ]
      }
    }

2.再次查询下一页，注意，这里查询时不需要指定index，只需要指定scroll\_id和本次的持续滚动时间。

**说白了，想要第几页，循环请求几次就行了，在设置的时间内scroll\_id是不会变的**

GET /_search/scroll?scroll=3s&scroll_id=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

或者

POST /_search/scroll
    {
     "scroll" : "3s",
     "scroll_id":"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"
    }

### 删除对应scroll\_id ###

当我们搜索完毕或者说已经滚动到最后的时候，我们可以选择删除scroll\_id

DELETE /_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

### 删除所有scroll\_id ###

DELETE /_search/scroll/_all

[ElasticSearch]: https://blog.csdn.net/gwd1154978352/article/details/82781731