ES索引Json格式字段设计

桃扇骨 2024-03-17 20:38 46阅读 0赞

### properties ###

[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/properties.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_properties.html]

#### 嵌套对象 ####

[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/object.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_object.html]

##### 创建索引 #####

curl --location --request PUT 'https://myhost/order_index' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "mappings": {
        
            "dynamic": "false",
            "properties": {
        
                "orderId": {
        
                    "type": "keyword"
                },
                "orderItems" : {
        
                	"properties": {
        
                		"itemType": {
        
                			"type": "keyword"
                		},
                		"itemName": {
        
                			"type": "keyword"
                		}
                	}
                }
            }
        }
    }'

##### 写数据 #####

curl --location --request PUT 'https://myhost/order_index/_doc/1' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "orderId": "1_1",
        "orderItems": [{
        
            "itemType": "food",
            "itemName": "egg"
        },
        {
        
            "itemType": "clothes",
            "itemName": "T-shirt"
        }
        ]
    }'
    
    curl --location --request PUT 'https://myhost/order_index/_doc/2' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "orderId": "2_2",
        "orderItems": [{
        
            "itemType": "food",
            "itemName": "pork"
        },
        {
        
            "itemType": "poultryEggs",
            "itemName": "egg"
        }
        ]
    }'

##### 读数据 #####

curl --location --request GET 'https://myhost/order_index/_search' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "query":{
        
            "bool":{
        
                "must":[
                    {
        
                        "match":{
        
                            "orderItems.itemType":"food"
                        }
                    },
                    {
        
                        "match":{
        
                            "orderItems.itemName":"egg"
                        }
                    }
                ]
            }
        }
    }'

查询结果

{
        
        "took": 763,
        "timed_out": false,
        "_shards": {
        
            "total": 5,
            "successful": 5,
            "skipped": 0,
            "failed": 0
        },
        "hits": {
        
            "total": {
        
                "value": 2,
                "relation": "eq"
            },
            "max_score": 0.723315,
            "hits": [
                {
        
                    "_index": "order_index",
                    "_type": "_doc",
                    "_id": "2",
                    "_score": 0.723315,
                    "_source": {
        
                        "orderId": "2_2",
                        "orderItems": [
                            {
        
                                "itemType": "food",
                                "itemName": "pork"
                            },
                            {
        
                                "itemType": "poultryEggs",
                                "itemName": "egg"
                            }
                        ]
                    }
                },
                {
        
                    "_index": "order_index",
                    "_type": "_doc",
                    "_id": "1",
                    "_score": 0.723315,
                    "_source": {
        
                        "orderId": "1_1",
                        "orderItems": [
                            {
        
                                "itemType": "food",
                                "itemName": "egg"
                            },
                            {
        
                                "itemType": "clothes",
                                "itemName": "T-shirt"
                            }
                        ]
                    }
                }
            ]
        }
    }

##### 优劣势 #####

1.  劣势：item对象中字段之间的映射关系丢弃了（官方文档有说明：[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/nested.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_nested.html]），通过两个字段检索数据得到的结果是“or”的关系，例如：案例中错误的检索结果：“orderItems.itemType”:“food” 或者 “orderItems.itemType”:“food”
2.  优势：底层实现简单，而且针对一对一场景，上述缺点不存在，即：案例中可以得到正确的结果 “orderItems.itemType”:“food” 并且 “orderItems.itemType”:“food”

tips：如果数据库中order与orderItems存储关系是一对一，那么使用嵌套对象没有任何问题。如果是一对多则检索会有问题，则只能选择下面的方案

##### 数据如何扁平化处理的？ #####

{
        
      "group" :        "fans",
      "user.first" : [ "alice", "john" ],
      "user.last" :  [ "smith", "white" ]
    }

#### 嵌套文档 ####

[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/nested.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_nested.html]

##### 创建索引 #####

curl --location --request PUT 'https://myhost/order_index' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "mappings": {
        
            "dynamic": "false",
            "properties": {
        
                "orderId": {
        
                    "type": "keyword"
                },
                "orderItems" : {
        
                	"type": "nested",
                	"properties": {
        
                		"itemType": {
        
                			"type": "keyword"
                		},
                		"itemName": {
        
                			"type": "keyword"
                		}
                	}
                }
            }
        }
    }'

##### 写数据 #####

同嵌套对象

##### 读数据 #####

curl --location --request GET 'https://myhost/order_index/_search' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "query": {
        
            "nested": {
        
                "path": "orderItems",
                "query": {
        
                    "bool": {
        
                        "must": [
                            {
        
                                "match": {
        
                                    "orderItems.itemType": "food"
                                }
                            },
                            {
        
                                "match": {
        
                                    "orderItems.itemName": "egg"
                                }
                            }
                        ]
                    }
                }
            }
        }
    }'

查询结果

{
        
        "took": 580,
        "timed_out": false,
        "_shards": {
        
            "total": 5,
            "successful": 5,
            "skipped": 0,
            "failed": 0
        },
        "hits": {
        
            "total": {
        
                "value": 1,
                "relation": "eq"
            },
            "max_score": 1.3862942,
            "hits": [
                {
        
                    "_index": "order_index",
                    "_type": "_doc",
                    "_id": "1",
                    "_score": 1.3862942,
                    "_source": {
        
                        "orderId": "1_1",
                        "orderItems": [
                            {
        
                                "itemType": "food",
                                "itemName": "egg"
                            },
                            {
        
                                "itemType": "clothes",
                                "itemName": "T-shirt"
                            }
                        ]
                    }
                }
            ]
        }
    }

##### 优劣势 #####

优势：可以解决嵌套对象的局限性，并且数据更精简，文档是独立存储的，不会冗余存储多份  
劣势：无法支持多级嵌套，例如：一个问题对应子级答案，答案对应子级投票（ES官方不建议使用该功能）。无法支持一个父多个子场景，例如：一个问题对应答案+评论  
例如如果存储多层级document会报错

curl --location --request PUT 'https://myhost/order_index/_doc/3' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "orderId": "3_3",
        "orderItems": [{
        
            "itemType": {
        
            	"myType": 1
            },
            "itemName": "egg"
        }
        ]
    }'

报错

{
        "error":{
        "root_cause":[{
        "type":"mapper_parsing_exception","reason":"failed to parse field [orderItems.itemType] of type [keyword] in document with id '3'. Preview of field's value: '{myType=1}'"}],"type":"mapper_parsing_exception","reason":"failed to parse field [orderItems.itemType] of type [keyword] in document with id '3'. Preview of field's value: '{myType=1}'","caused_by":{
        "type":"illegal_state_exception","reason":"Can't get text on a START_OBJECT at 4:21"}},"status":400}

##### 数据如何存储的？ #####

官方文档中有描述，嵌套文档是独立的document，因此上述案例中实际底层存储了6个document，使用cat名称可以看到实际也是如此  
![截屏2023-06-27 13.51.43.png][2023-06-27 13.51.43.png]

### Join ###

官方文档案例很详细，不再搬运了，详情参考：[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/parent-join.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_parent-join.html]

##### 优劣势 #####

优势：可以支持一个父document对应多个子document（数据结构不一样的子文档），也可以支持多级关系（官方不推荐使用）  
劣势：join实现成本高，需要花费更高的服务资源，cpu，内存

### Ingest Pipeline ###

成本较高，需要增加Ingest节点，本文不再关注，详情参数官方文档：[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/json-processor.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_json-processor.html]

### 总结 ###

1.  properties嵌套对象，基本满足的大部分需求，并且实现简单
2.  properties嵌套索引，查询用法会有些差异，如果子properties对于数组json的检索场景要求对象字段之间匹配关系是与运算关系（and关系），则需要使用该类型
3.  子properties的字段可以动态添加，如果dynamic=false新增的字段不能用于检索，新增字段想要用于检索需要reindex，如果dynamic=true新增的字段可以用于检索，例如：下面案例，新增itemId字段可以直接用检索，dynamic=true时。

curl --location --request PUT 'https://myhost/order_index/_doc/3' \
    --header 'Content-Type: application/json' \
    --data '{
        
        "orderId": "2_1",
        "orderItems": [{
        
            "itemType": "food",
            "itemName": "pork",
            "itemId": 2
        }]
    }'

注意，子对象如果没有指定dynamic将继承父的设置，详情可以参考官方文档：[https://www.elastic.co/guide/en/elasticsearch/reference/8.8/dynamic.html][https_www.elastic.co_guide_en_elasticsearch_reference_8.8_dynamic.html]

[https_www.elastic.co_guide_en_elasticsearch_reference_8.8_properties.html]: https://www.elastic.co/guide/en/elasticsearch/reference/8.8/properties.html
[https_www.elastic.co_guide_en_elasticsearch_reference_8.8_object.html]: https://www.elastic.co/guide/en/elasticsearch/reference/8.8/object.html
[https_www.elastic.co_guide_en_elasticsearch_reference_8.8_nested.html]: https://www.elastic.co/guide/en/elasticsearch/reference/8.8/nested.html
[2023-06-27 13.51.43.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/61ecbea78eec4f8daebe0d6b76f20a25.png
[https_www.elastic.co_guide_en_elasticsearch_reference_8.8_parent-join.html]: https://www.elastic.co/guide/en/elasticsearch/reference/8.8/parent-join.html
[https_www.elastic.co_guide_en_elasticsearch_reference_8.8_json-processor.html]: https://www.elastic.co/guide/en/elasticsearch/reference/8.8/json-processor.html
[https_www.elastic.co_guide_en_elasticsearch_reference_8.8_dynamic.html]: https://www.elastic.co/guide/en/elasticsearch/reference/8.8/dynamic.html