elasticsearch 实现查询忽略大小写

背景：在搜索的时候经常会有一种场景就是忽略大小写，不管你输入的是全大写还是全小写还是大小写混合，希望都能够搜索出结果。

解决思路：Elasticsearch中的lowercase normalizer将文本转换为小写，并将其作为规范形式存储在索引中。这可以确保在搜索和比较文本时忽略大写字母的差异，从而提高搜索的准确性和一致性

实现方案:

开发过程中，经常会遇到索引是之前已经建好的，由于es的规则，只能新增字段，不能删除或者修改已经存在的字段，可以动态更新原有索引的setting，动态更新setting，需要先关闭索引，执行玩更新操作以后，再开启索引,步骤如下：

index_name是 索引名称

field_name是字段名称

POST index_name/_close
PUT /index_name/_settings
{
  "index":{
    "analysis":{
      "normalizer":{
        "lowercase_normalizer":{
          "type": "custom",
          "char_filter": [],
           "filter": ["lowercase"]
        }
      }
    }
  }
}
POST index_name/_open

PUT /index_name/_mapping
{
    "properties" : {
      "field_name" : {
        "type" : "keyword",
        "normalizer":"lowercase_normalizer"
      }
    }

}

举个例子：

新建一个索引：

PUT /lowercase_normalizer_index
{
    "mappings" : {
      "properties" : {
        "id" : {
          "type" : "keyword"
        }
      }
    }
}

新增字段 设置属性

POST lowercase_normalizer_index/_close
PUT /lowercase_normalizer_index/_settings
{
  "index":{
    "analysis":{
      "normalizer":{
        "lowercase_normalizer":{
          "type": "custom",
          "char_filter": [],
           "filter": ["lowercase"]
        }
      }
    }
  }
}
POST lowercase_normalizer_index/_open

PUT /lowercase_normalizer_index/_mapping
{
    "properties" : {
      "name" : {
        "type" : "keyword",
        "normalizer":"lowercase_normalizer"
      }
    }
}

插入一些数据

PUT lowercase_normalizer_index/_doc/1
{
  "id": "1",
  "name": "Mohammed Ahmed"
}


PUT lowercase_normalizer_index/_doc/2
{
"id": "2",
"name": "Sophie Martin"
}


PUT lowercase_normalizer_index/_doc/3
{
  "id": "3",
  "name": "mohammed ahmed"
}

验证

GET lowercase_normalizer_index/_search
{
  "query": {
    "wildcard": {
      "name": {
        "value": "*moham*"
      }
    }
  }
}

结果

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "lowercase_normalizer_index",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "id" : "1",
          "name" : "Mohammed Ahmed"
        }
      },
      {
        "_index" : "lowercase_normalizer_index",
        "_type" : "_doc",
        "_id" : "3",
        "_score" : 1.0,
        "_source" : {
          "id" : "3",
          "name" : "mohammed ahmed"
        }
      }
    ]
  }
}