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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>

Prerequisites

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If the Elasticsearch security features are enabled, you must have the view_index_metadata, read, or manage index privilege for the target data stream, index, or alias.

Description

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

The field capabilities API returns runtime fields like any other field. For example, a runtime field with a type of keyword is returned as any other field that belongs to the keyword family.

Path parameters

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<target>: (Optional, string) Comma-separated list of data streams, indices, and aliases used to limit the request. Supports wildcards (*). To target all data streams and indices, omit this parameter or use * or _all.

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 if any wildcard expression, index alias, or _all value targets only missing or closed indices. This behavior applies even if the request targets other open indices. For example, a request targeting foo*,bar* returns an error if an index starts with foo but no index starts with bar.

Defaults to true.

expand_wildcards

(Optional, string) Type of index that wildcard patterns can match. If the request can target data streams, this argument determines whether wildcard expressions match hidden data streams. Supports comma-separated values, such as open,hidden. Valid values are:

all: Match any data stream or index, including hidden ones.
open: Match open, non-hidden indices. Also matches any non-hidden data stream.
closed: Match closed, non-hidden indices. Also matches any non-hidden data stream. Data streams cannot be closed.
hidden: Match hidden data streams and hidden indices. Must be combined with open, closed, or both.
none: Wildcard patterns 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.
runtime_mappings: (Optional, object) Defines ad-hoc runtime fields in the request similar to the way it is done in search requests. These fields exist only as part of the query and take precedence over fields defined with the same name in the index mappings.

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.

metadata_field: Whether this field is registered as a metadata field.
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": {
        "metadata_field": false,
        "searchable": true,
        "aggregatable": false,
        "indices": [ "index1", "index2" ],
        "non_aggregatable_indices": [ "index1" ]  
      },
      "keyword": {
        "metadata_field": false,
        "searchable": false,
        "aggregatable": true,
        "indices": [ "index3", "index4" ],
        "non_searchable_indices": [ "index4" ]    
      }
    },
    "title": {                                    
      "text": {
        "metadata_field": false,
        "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": {
        "metadata_field": false,
        "searchable": true,
        "aggregatable": false,
        "indices": [ "index1", "index2" ],
        "non_aggregatable_indices": [ "index1" ]
      },
      "keyword": {
        "metadata_field": false,
        "searchable": false,
        "aggregatable": true,
        "indices": [ "index3", "index4" ],
        "non_searchable_indices": [ "index4" ]
      },
      "unmapped": {                               
        "metadata_field": false,
        "indices": [ "index5" ],
        "searchable": false,
        "aggregatable": false
      }
    },
    "title": {
      "text": {
        "metadata_field": false,
        "indices": [ "index1", "index2", "index3", "index4" ],
        "searchable": true,
        "aggregatable": false
      },
      "unmapped": {                               
        "metadata_field": false,
        "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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