ElasticSearch nested parent/child join

妖狐艹你老母 2024-04-17 06:24 73阅读 0赞

# ElasticSearch  nested parent/child join #

ElasticSearch  7.2.0

1、创建索引含有nested类型的索引

2、添加数据（nested）

3、查询（nested）

4、创建含有关联关系的索引

5、添加数据（parent/child join）

5.1 添加父文档  
   5.2 添加子文档

6、查询（parent/child join）

6.1 Parent Id 查询  
   6.2 Has Child 查询  
   6.3 Has Parent 查询  
   6.4 通过ID和routing

7、nested VS parent/child join

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[https://www.cbedai.net/u014646662][Link 1]

## 1、创建索引含有nested类型的索引 ##

PUT my_blogs_nested
    {
      "settings": {
        "number_of_shards": 3,
        "number_of_replicas": 0
      },
      "mappings": {
        "properties": {
          "blog_comments_relation":{
            
              "type" : "nested",
              "properties" : {
                "comment" : {
                  "type" : "text",
                  "norms" : false,
                  "fields" : {
                    "keyword" : {
                      "type" : "keyword"
                    }
                  }
                },
                "username" : {
                  "type" : "text",
                  "norms" : false,
                  "fields" : {
                    "keyword" : {
                      "type" : "keyword"
                    }
                  }
                }
              }
            
          },
          "content":{
            "type":"text"
          },
          "title":{
            "type":"text",
            "norms":false,
            "fields": {
              "keyword":{
                "type":"keyword"
              }
            }
          } 
        }
      }
    }

## 2、添加数据（nested） ##

PUT my_blogs_nested/_doc/blog1
    {
      "title":"Learning ElasticSearch",
      "content":"Learning Elastic Stack",
      "blog_comments_relation":[
        {
          "comment":"I am learning Elatsic Stack",
          "username":"Lucky"
        },{
          "comment":"Hello ElasticSearch",
          "username":"Bob"
        }
      ]
    }
    
    PUT my_blogs_nested/_doc/blog2
    {
      "title":"Leaning Hadoop",
      "content":"Leaning Hadoop",
      "blog_comments_relation":[
        {
          "comment":"I am learning Hadoop",
          "username":"Lucy"
        },{
          "comment":"Hello Hadoop",
          "username":"Bob"
        }
      ]
    }

## 3、查询（nested） ##

#查看索引
    GET my_blogs_nested
    
    #查询文档
    GET my_blogs_nested/_search
    {
      "query": {
        "nested": {
          "path": "blog_comments_relation",
          "query": {
            "match": {
              "blog_comments_relation.username": "lucy"
            }
          }
        }
      }
    }

## 4、创建含有关联关系的索引 ##

"blog":"comment"，即父文档是blog，子文档是comment，子文档可以有多个（一对多的关系）

PUT my_blogs
    {
      "settings": {
        "number_of_shards": 3,
        "number_of_replicas": 0
      },
      "mappings": {
        "properties": {
          "blog_comments_relation":{
            "type": "join",
            "relations":{
              "blog":"comment"
            }
          },
          "content":{
            "type":"text"
          },
          "title":{
            "type":"text",
            "norms":false,
            "fields": {
              "keyword":{
                "type":"keyword"
              }
            }
          } 
        }
      }
    }

## 5、添加数据（parent/child join） ##

### 5.1 添加父文档 ###

"name":"blog" 父文档名

PUT my_blogs/_doc/blog1
    {
      "title":"Learning ElasticSearch",
      "content":"Learning Elastic Stack",
      "blog_comments_relation":{
        "name":"blog"
      }
    }
    
    PUT my_blogs/_doc/blog2
    {
      "title":"Leaning Hadoop",
      "content":"Leaning Hadoop",
      "blog_comments_relation":{
        "name":"blog"
      }
    }

### 5.2 添加子文档 ###

"name":"comment", 子文档名  
 "parent":"blog1"，指定父文档的ID

routing=blog1，子文档和父文档必须在同一个分片上，路由到父文档的ID

PUT my_blogs/_doc/comment3?routing=blog2
    {
      "comment":"Hello Hadoop",
      "username":"Bob",
      "blog_comments_relation":{
        "name":"comment",
        "parent":"blog2"
      }
    }
    
    PUT my_blogs/_doc/comment4?routing=blog1
    {
      "comment":"Hello ElasticSearch",
      "username":"Bob",
      "blog_comments_relation":{
        "name":"comment",
        "parent":"blog1"
      }
    }

## 6、查询（parent/child join） ##

### 6.1 Parent Id 查询 ###

GET my_blogs/_search
    {
      "query": {
        "parent_id":{
          "type":"comment",
          "id":"blog2"
        }
      }
    }

### 6.2 Has Child 查询,返回父文档 ###

GET my_blogs/_search
    {
      "query": {
        "has_child": {
          "type": "comment",
          "query": {
            "match": {
              "username": "lucky"
            }
          }
        }
      }
    }

### 6.3 Has Parent 查询，返回相关的子文档 ###

GET my_blogs/_search
    {
      "query": {
        "has_parent": {
          "parent_type": "blog",
          "query": {
            "match": {
              "content": "elastic"
            }
          }
        }
      }
    }

### 6.4 通过ID和routing ，访问子文档(不加routing查不到) ###

GET my_blogs/_doc/comment3?routing=blog2

## 7、 nested VS parent/child join ##

<table> 
 <thead> 
  <tr> 
   <th>&nbsp;</th> 
   <th style="width:348px;">nested</th> 
   <th style="width:365px;">parent/child join</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <th>优点</th> 
   <td style="width:348px;">读取性能高</td> 
   <td style="width:365px;">父子文档可以独立更新</td> 
  </tr> 
  <tr> 
   <th>缺点</th> 
   <td style="width:348px;">每次更新需要更新整个文档</td> 
   <td style="width:365px;">关联关系，需要额外的内存，查询效率相对较差</td> 
  </tr> 
  <tr> 
   <th>场景</th> 
   <td style="width:348px;">频繁查询</td> 
   <td style="width:365px;">频繁更新</td> 
  </tr> 
 </tbody> 
</table>

[Link 1]: https://www.cbedai.net/u014646662