Exists Query属于Term-level Query查询, 查询某字段值不为空的文档。脑图如下：

内容说明：

本文内容同微信公众号【凡登】，关注不迷路，欢迎加入一起共同学习。原文链接:Terms-level Query之Exists Query

一、语法：

1、检索字段上存在值的文档

2、检索字段上不存在值的文档

二、Exists Query示例

0、数据准备

1、当字段值为空的演示示例：

2、当index:false情况下演示示例

3、mapping设置ignore_above演示示例

4、mapping设置ignore_malformed演示示例

三、总结：

官方文档：

https://www.elastic.co/guide/en/elasticsearch/reference/7.13/query-dsl-exists-query.html

一、语法：

1、`检索字段上存在值的文档`

GET /_search{  "query": {    "exists": {      "field": <field_name>    }  }}

参数说明：

field : 被检索的字段

通过bool改变Exists查询方式进行反向查询，即查询字段不存在值的文档。

`2、检索字段上不存在值的文档`

语法：

GET /_search{  "query": {    "bool": {      "must_not": {        "exists": {          "field": <field_name>        }      }    }  }}

二、Exists Query示例

通过Exists Query可以查询字段值不为空的文档，那么在以下情况下

比如：

source中值可能为null, []
字段mapping参数index:false
字段值长度超过mapping中定义的ignore_above
当mapping中设置ignore_malformed，文档中字段值类型与mapping中定义的不一致

那么此时Exists Query会有什么样的表现？

0、数据准备

通过示例验证，演示数据准备如下：

DELETE exists_query_demo_index_001
// 以下样例数据经过特殊设计，用于后续检索使用，// name字段用于验证空值// address 字段用于验证 index:false// content 字段用于验证ignore_above// age 字段用于验证ignore_malformed# 定义mappingPUT exists_query_demo_index_001{  "mappings": {    "properties": {      "name":{        "type":"keyword",        "fields": {          "null_value":{            "type":"keyword",            "null_value": "NULL" // 自定义空值          },          "text_value":{            "type":"text"          }        }      },      "address":{        "type":"text",        "fields": {          "keyword_value_index_false":{            "type":"keyword",            "index": false  // index设置为false,即不被索引          },           "text_value_index_false":{            "type":"text",            "index": false          }        }      },      "content":{        "type":"keyword",        "ignore_above": 8  // 忽略字符长度大于8字段      },      "age":{        "type":"integer",        "ignore_malformed": true  // 忽略值异常字段值      }    }  }}// 批量写入文档POST exists_query_demo_index_001/_bulk?refresh=true{"index":{"_id":1}}{"name":"Fan","address":"BJ_1","content":"helloFan","age":17}{"index":{"_id":2}}{"name":"Deng","address":"BJ_2","content":"helloDeng","age":"18岁"}{"index":{"_id":3}}{"name":"FanDeng","address":"BJ_3","content":"helloFanDeng","age":19}{"index":{"_id":4}}{"name":"","address":"BJ_4","content":"hello_","age":"20岁"}{"index":{"_id":5}}{"name":null,"address":"BJ_5","content":"hello_null","age":21}{"index":{"_id":6}}{"name":"NULL","address":"BJ_6","content":"hello_NULL","age":22}{"index":{"_id":7}}{"name":[],"address":"BJ_7","content":"hello_[]","age":"23岁"}{"index":{"_id":8}}{"name":[""],"address":"BJ_8","content":"hello_[empty_char]","age":24}{"index":{"_id":9}}{"name":[null],"address":"BJ_9","content":"hello_[null]","age":25}{"index":{"_id":10}}{"name":["NULL"],"address":"BJ_10","content":"hello_[NULL]","age":26}{"index":{"_id":11}}{"name":["","Fan"],"address":"BJ_11","content":"hello_[empty_char,Fan]","age":27}{"index":{"_id":12}}{"name":[null,"Fan"],"address":"BJ_12","content":"hello_[null,Fan]","age":28}{"index":{"_id":13}}{"name":["NULL","Fan"],"address":"BJ_13","content":"hello_[NULL,Fan]","age":29}//查询数据是否写入GET exists_query_demo_index_001/_search{  "track_total_hits": true, // 显示检索数据的记录数  "size": 0  // 不显示source}结果：{  "took" : 0,  "timed_out" : false,  "_shards" : {    "total" : 1,    "successful" : 1,    "skipped" : 0,    "failed" : 0  },  "hits" : {    "total" : {      "value" : 13,  // 13条数据全部写入      "relation" : "eq" //     },    "max_score" : null,    "hits" : [ ]  }}

1、当字段值为空的演示示例：

GET exists_query_demo_index_001/_search{  "track_total_hits": true,   "size": 20,   "query": {    "exists": {      "field": "name"    }  }}结果显示：id为5，7，9的文档name不存在值即当字段值为null, 空数组[]或[null] 的时候，Exists Query检索不到相关文档以下query检查与上述查询结果相通GET exists_query_demo_index_001/_search{  "track_total_hits": true,   "size": 20,   "query": {    "exists": {      "field": "name.text_value"    }  }}即类型为keyword以及text的字段，Exists Query查询结果相同我们通过反向查询看看字段name不存在值的文档有哪些GET exists_query_demo_index_001/_search{  "track_total_hits": true,   "query": {    "bool": {      "must_not": [        {          "exists": {            "field": "name"          }        }      ]    }  }}结果:{  "took" : 0,  "timed_out" : false,  "_shards" : {    "total" : 1,    "successful" : 1,    "skipped" : 0,    "failed" : 0  },  "hits" : {    "total" : {      "value" : 3,      "relation" : "eq"    },    "max_score" : 0.0,    "hits" : [      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "5",        "_score" : 0.0,        "_source" : {          "name" : null,          "address" : "BJ_5",          "content" : "hello_null",          "age" : 21        }      },      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "7",        "_score" : 0.0,        "_ignored" : [          "age"        ],        "_source" : {          "name" : [ ],          "address" : "BJ_7",          "content" : "hello_[]",          "age" : "23岁"        }      },      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "9",        "_score" : 0.0,        "_source" : {          "name" : [            null          ],          "address" : "BJ_9",          "content" : "hello_[null]",          "age" : 25        }      }    ]  }}GET exists_query_demo_index_001/_search{  "track_total_hits": true,   "size": 20,   "query": {    "exists": {      "field": "name.null_value"    }  }}结果显示：id为7的文档name不存在值即当字段值为 空数组[] 的时候，Exists Query检索不到相关文档字段name.null_value为自定义空值，当字段值出现空值的时候会填充自定义的默认值，故当检查到null 实际填充值为 NULL

小结：

即当字段值为null, 空数组[]或[null] 的时候，Exists Query检索不到相关文档，

如果自定义了空值，那么仅字段值空数组[]下，Exists Query检索不到相关文档

2、当index:false情况下演示示例

GET exists_query_demo_index_001/_search{  "size": 20,   "query": {    "exists": {      "field": "address"    }  }}结果：所有文档的address字段均存在值，GET exists_query_demo_index_001/_search{  "size": 20,   "query": {    "exists": {      "field": "address.keyword_index_false"    }  }}结果：所有文档的address字段均不存在值，GET exists_query_demo_index_001/_search{  "size": 20,   "query": {    "exists": {      "field": "address.text_index_false"    }  }}结果：所有文档的address字段均不存在值，

小结：当index:false时，所有文档的address字段均不存在值，Exists Query检索不到相关文档

3、mapping设置ignore_above演示示例

GET exists_query_demo_index_001/_search{  "size": 20,   "query": {    "exists": {      "field": "content"    }  }}结果:{  "took" : 0,  "timed_out" : false,  "_shards" : {    "total" : 1,    "successful" : 1,    "skipped" : 0,    "failed" : 0  },  "hits" : {    "total" : {      "value" : 3,      "relation" : "eq"    },    "max_score" : 1.0,    "hits" : [      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "1",        "_score" : 1.0,        "_source" : {          "name" : "Fan",          "address" : "BJ_1",          "content" : "helloFan",          "age" : 17        }      },      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "4",        "_score" : 1.0,        "_ignored" : [          "age"        ],        "_source" : {          "name" : "",          "address" : "BJ_4",          "content" : "hello_",          "age" : "20岁"        }      },      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "7",        "_score" : 1.0,        "_ignored" : [          "age"        ],        "_source" : {          "name" : [ ],          "address" : "BJ_7",          "content" : "hello_[]",          "age" : "23岁"        }      }    ]  }}

小结：

当字段值超过ignore_above配置的长度时，Exists Query检索不到相关文档

4、mapping设置ignore_malformed演示示例

GET exists_query_demo_index_001/_search{  "size": 20,   "query": {    "exists": {      "field": "age"    }  }}通过反向查询看看有哪些age字段不存在值的文档GET exists_query_demo_index_001/_search{  "track_total_hits": true,   "query": {    "bool": {      "must_not": [        {          "exists": {            "field": "age"          }        }      ]    }  }}结果：{  "took" : 0,  "timed_out" : false,  "_shards" : {    "total" : 1,    "successful" : 1,    "skipped" : 0,    "failed" : 0  },  "hits" : {    "total" : {      "value" : 3,      "relation" : "eq"    },    "max_score" : 0.0,    "hits" : [      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "2",        "_score" : 0.0,        "_ignored" : [          "age"        ],        "_source" : {          "name" : "Deng",          "address" : "BJ_2",          "content" : "helloDeng",          "age" : "18岁"        }      },      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "4",        "_score" : 0.0,        "_ignored" : [          "age"        ],        "_source" : {          "name" : "",          "address" : "BJ_4",          "content" : "hello_",          "age" : "20岁"        }      },      {        "_index" : "exists_query_demo_index_001",        "_type" : "_doc",        "_id" : "7",        "_score" : 0.0,        "_ignored" : [          "age"        ],        "_source" : {          "name" : [ ],          "address" : "BJ_7",          "content" : "hello_[]",          "age" : "23岁"        }      }    ]  }}