WARNING: Version 6.0 of Elasticsearch has passed its EOL date.

This documentation is no longer being maintained and may be removed. If you are running this version, we strongly advise you to upgrade. For the latest information, see the current release documentation.

« _all field _id field »
Elastic Docs ›Elasticsearch Reference [6.0] ›Mapping ›Meta-Fields

_field_names field

edit

_field_names field

edit

The _field_names field indexes the names of every field in a document that contains any value other than null. This field is used by the exists query to find documents that either have or don’t have any non-null value for a particular field.

The value of the _field_names field is accessible in queries:

# Example documents
PUT my_index/my_type/1
{
  "title": "This is a document"
}

PUT my_index/my_type/2?refresh=true
{
  "title": "This is another document",
  "body": "This document has a body"
}

GET my_index/_search
{
  "query": {
    "terms": {
      "_field_names": [ "title" ] 
    }
  }
}

Querying on the _field_names field (also see the exists query)

Disabling _field_names

edit

Because _field_names introduce some index-time overhead, you might want to disable this field if you want to optimize for indexing speed and do not need exists queries.

PUT tweets
{
  "mappings": {
    "tweet": {
      "_field_names": {
        "enabled": false
      }
    }
  }
}
« _all field _id field »