# Evaluate ranked search results


**POST /{index}/_rank_eval**

**All methods and paths for this operation:**

<div>
                      <span class="operation-verb get">GET</span>
                      <span class="operation-path">/_rank_eval</span>
                      </div>
                    <div>
                      <span class="operation-verb post">POST</span>
                      <span class="operation-path">/_rank_eval</span>
                      </div>
                    <div>
                      <span class="operation-verb get">GET</span>
                      <span class="operation-path">/{index}/_rank_eval</span>
                      </div>
                    <div>
                      <span class="operation-verb post">POST</span>
                      <span class="operation-path">/{index}/_rank_eval</span>
                      </div>
                    

Evaluate the quality of ranked search results over a set of typical search queries.

## Required authorization

* Index privileges: `read`


[More about ranking evaluation](https://www.elastic.co/docs/reference/elasticsearch/rest-apis/search-rank-eval)

## Servers
- http://api.example.com: http://api.example.com ()


## Authentication methods
- Api key auth
- Basic auth
- Bearer auth


## Parameters

### Path parameters
- **index** (string | array[string])
  A  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
- **allow_no_indices** (boolean)
  A setting that does two separate checks on the index expression.
  If `false`, the request returns an error (1) if any wildcard expression
  (including `_all` and `*`) resolves to zero matching indices or (2) if the
  complete set of resolved indices, aliases or data streams is empty after all
  expressions are evaluated. If `true`, index expressions that resolve to no
  indices are allowed and the request returns an empty result.
- **expand_wildcards** (string | array[string])
  Whether to expand wildcard expression to concrete indices that are open, closed or both.

  Supported values include:
    - `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 expressions are not accepted.

- **ignore_unavailable** (boolean)
  If `false`, the request returns an error if it targets a concrete (non-wildcarded)
  index, alias, or data stream that is missing, closed, or otherwise unavailable.
  If `true`, unavailable concrete targets are silently ignored.
- **search_type** (string)
  Search operation type

  Supported values include:
    - `query_then_fetch`: Documents are scored using local term and document frequencies for the shard. This is usually faster but less accurate.
    - `dfs_query_then_fetch`: Documents are scored using global term and document frequencies across all shards. This is usually slower but more accurate.


### Body: application/json (object)

- **requests** (array[object])
  A set of typical search requests, together with their provided ratings.
- **metric** (object)
  Definition of the evaluation metric to calculate.


## Responses
### 200


#### Body: application/json (object)
- **metric_score** (number)
  The overall evaluation quality calculated by the defined metric
- **details** (object)
  The details section contains one entry for every query in the original requests section, keyed by the search request id
- **failures** (object)



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