You're viewing version 2.17 of the OpenSearch documentation. This version is no longer maintained. For the latest version, see the current documentation. For information about OpenSearch version maintenance, see Release Schedule and Maintenance Policy.

Field names

The _field_names field indexes field names that contain non-null values. This enables the use of the exists query, which can identify documents that either have or do not have non-null values for a specified field.

However, _field_names only indexes field names when both doc_values and norms are disabled. If either doc_values or norms are enabled, then the exists query still functions but will not rely on the _field_names field.

Mapping example

{
    "mappings": {
       "_field_names": {
        "enabled": "true"
      },
    "properties": {
      },
      "title": {
        "type": "text",
        "doc_values": false,
        "norms": false
      },
      "description": {
        "type": "text",
        "doc_values": true,
        "norms": false
      },
      "price": {
        "type": "float",
        "doc_values": false,
        "norms": true
      }
    }
  }
}