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Field capabilities API

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Field capabilities API

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Allows you to retrieve the capabilities of fields among multiple indices. For data streams, the API returns field capabilities among the stream’s backing indices.

GET /_field_caps?fields=rating

Request

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GET /_field_caps?fields=<fields>

POST /_field_caps?fields=<fields>

GET /<target>/_field_caps?fields=<fields>

POST /<target>/_field_caps?fields=<fields>

Description

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The field capabilities API returns the information about the capabilities of fields among multiple indices.

Path parameters

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<target>

(Optional, string) Comma-separated list of data streams, indices, and index aliases used to limit the request. Wildcard expressions (*) are supported.

To target all data streams and indices in a cluster, omit this parameter or use _all or *.

Query parameters

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fields

(Required, string) Comma-separated list of fields to retrieve capabilities for. Wildcard (*) expressions are supported.

allow_no_indices

(Optional, Boolean) If false, the request returns an error when a wildcard expression, index alias, or _all value targets only missing or closed indices.

Defaults to true.

expand_wildcards

(Optional, string) Controls what kind of indices that wildcard expressions can expand to. Multiple values are accepted when separated by a comma, as in open,hidden. Valid values are:

all: Expand to open and closed indices, including hidden indices.
open: Expand only to open indices.
closed: Expand only to closed indices.
hidden: Expansion of wildcards will include hidden indices. Must be combined with open, closed, or both.
none: Wildcard expressions are not accepted.

Defaults to open.

ignore_unavailable

(Optional, Boolean) If false, the request returns an error if it targets a missing or closed index. Defaults to false.

include_unmapped

(Optional, Boolean) If true, unmapped fields are included in the response. Defaults to false.

Request body

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index_filter: (Optional, query object Allows to filter indices if the provided query rewrites to match_none on every shard.

Response body

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The types used in the response describe families of field types. Normally a type family is the same as the field type declared in the mapping, but to simplify matters certain field types that behave identically are described using a type family. For example, keyword, constant_keyword and wildcard field types are all described as the keyword type family.

searchable: Whether this field is indexed for search on all indices.
aggregatable: Whether this field can be aggregated on all indices.
indices: The list of indices where this field has the same type family, or null if all indices have the same type family for the field.
non_searchable_indices: The list of indices where this field is not searchable, or null if all indices have the same definition for the field.
non_aggregatable_indices: The list of indices where this field is not aggregatable, or null if all indices have the same definition for the field.
meta: Merged metadata across all indices as a map of string keys to arrays of values. A value length of 1 indicates that all indices had the same value for this key, while a length of 2 or more indicates that not all indices had the same value for this key.

Examples

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The request can be restricted to specific data streams and indices:

GET my-index-000001/_field_caps?fields=rating

The next example API call requests information about the rating and the title fields:

GET _field_caps?fields=rating,title

The API returns the following response:

{
  "indices": [ "index1", "index2", "index3", "index4", "index5" ],
  "fields": {
    "rating": {                                   
      "long": {
        "searchable": true,
        "aggregatable": false,
        "indices": [ "index1", "index2" ],
        "non_aggregatable_indices": [ "index1" ]  
      },
      "keyword": {
        "searchable": false,
        "aggregatable": true,
        "indices": [ "index3", "index4" ],
        "non_searchable_indices": [ "index4" ]    
      }
    },
    "title": {                                    
      "text": {
        "searchable": true,
        "aggregatable": false

      }
    }
  }
}

	The field `rating` is defined as a long in `index1` and `index2` and as a `keyword` in `index3` and `index4`.
	The field `rating` is not aggregatable in `index1`.
	The field `rating` is not searchable in `index4`.
	The field `title` is defined as `text` in all indices.

By default unmapped fields are ignored. You can include them in the response by adding a parameter called include_unmapped in the request:

GET _field_caps?fields=rating,title&include_unmapped

In which case the response will contain an entry for each field that is present in some indices but not all:

{
  "indices": [ "index1", "index2", "index3" ],
  "fields": {
    "rating": {
      "long": {
        "searchable": true,
        "aggregatable": false,
        "indices": [ "index1", "index2" ],
        "non_aggregatable_indices": [ "index1" ]
      },
      "keyword": {
        "searchable": false,
        "aggregatable": true,
        "indices": [ "index3", "index4" ],
        "non_searchable_indices": [ "index4" ]
      },
      "unmapped": {                               
        "indices": [ "index5" ],
        "searchable": false,
        "aggregatable": false
      }
    },
    "title": {
      "text": {
        "indices": [ "index1", "index2", "index3", "index4" ],
        "searchable": true,
        "aggregatable": false
      },
      "unmapped": {                               
        "indices": [ "index5" ],
        "searchable": false,
        "aggregatable": false
      }
    }
  }
}

	The `rating` field is unmapped` in `index5`.
	The `title` field is unmapped` in `index5`.

It is also possible to filter indices with a query:

POST my-index-*/_field_caps?fields=rating
{
  "index_filter": {
    "range": {
      "@timestamp": {
        "gte": "2018"
      }
    }
  }
}

In which case indices that rewrite the provided filter to match_none on every shard will be filtered from the response.

The filtering is done on a best-effort basis, it uses index statistics and mappings to rewrite queries to match_none instead of fully executing the request. For instance a range query over a date field can rewrite to match_none if all documents within a shard (including deleted documents) are outside of the provided range. However, not all queries can rewrite to match_none so this API may return an index even if the provided filter matches no document.

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