elasticsearch null查询，为null设置默认值

首先需要确定的是，之所以能够设置null_value 一定是你在index数据的时候传递了这个字段，只不过数据是null，text类型不支持设置null_value
https://www.elastic.co/guide/en/elasticsearch/reference/current/null-value.html

1. 创建index

PUT testnumber
{
  "mappings": {
    "properties": {
      "test":
      {
        "type": "nested",
        "properties": {
          "age":
          {
            "type":"double",
            "null_value":"-999999"
          },
          "ttt":{
            "type":"keyword",
            "null_value":"None"
          }
        }
      }
    }
  }
}

2. 插入数据

PUT testnumber/_doc/1
{
  "test":{"age":0,"ttt":null}
}

PUT testnumber/_doc/2
{
  "test":{"age":0.0}
}

3. null查询

GET testnumber/_search
{
  "query": {
    "nested": {
      "path": "test",
      "query": {
        "term": {
          "test.ttt": {
            "value": "None"
          }
        }
      }
    }
  }
}