原英文版地址: https://www.elastic.co/guide/en/elasticsearch/reference/7.7/null-value.html, 原文档版权归 www.elastic.co 所有
本地英文版地址: ../en/null-value.html
重要: 此版本不会发布额外的bug修复或文档更新。最新信息请参考 当前版本文档。
Elasticsearch Guide [7.7] » Mapping » Mapping parameters » null_value
« norms position_increment_gap »

null_valueedit

A null value cannot be indexed or searched. When a field is set to null, (or an empty array or an array of null values) it is treated as though that field has no values.

The null_value parameter allows you to replace explicit null values with the specified value so that it can be indexed and searched. For instance:

PUT my_index
{
  "mappings": {
    "properties": {
      "status_code": {
        "type":       "keyword",
        "null_value": "NULL" 
      }
    }
  }
}

PUT my_index/_doc/1
{
  "status_code": null
}

PUT my_index/_doc/2
{
  "status_code": [] 
}

GET my_index/_search
{
  "query": {
    "term": {
      "status_code": "NULL" 
    }
  }
}

Replace explicit null values with the term NULL.

An empty array does not contain an explicit null, and so won’t be replaced with the null_value.

A query for NULL returns document 1, but not document 2.

The null_value needs to be the same datatype as the field. For instance, a long field cannot have a string null_value.

The null_value only influences how data is indexed, it doesn’t modify the _source document.

« norms position_increment_gap »