Elasticsearch what's the difference between null and empty value?-CodePudding

I have a mapping, like this

{
  "properties": {
    "id": {
      "type": "keyword"
    },
    "name": {
      "type": "keyword"
    }
  }
}

about name field, in my original data the name can be empty "". I have two choose to put the doc to ES:

{
    "id" : 6 ,
    "name" : ""
}

{
    "id" : 6 ,
    "name" : null
}

I don't need to search data like name == "" or name != "" or name == null or name != null.

I saw that a mount of empty values will cause the performance problem somewhere else. And saw that null value will not be index and search. So I want to put null field.

Is there any difference in my use case ?

CodePudding user response：

A field with an empty "" string value will yield true to an exists query, which means that even if your value doesn't really contain a value, for Elasticsearch it does.

The only way to tell ES that your field doesn't contain a value is by assigning null.

CodePudding user response：

An empty string is a string instance of zero length, whereas a null string has no value at all.