anchor.diff:  [cols="<,<",options="header",]
   |=======================================================================
   |Parameter |Description
  +|`k` |sets the maximum number of documents retrieved per query. This value will act in place of the usual `size` parameter 
  +in the query. Defaults to 10.
   |`relevant_rating_threshold` |Sets the rating threshold above which documents are considered to be
   "relevant". Defaults to `1`.
   |=======================================================================
  
positive.code: returns typical information retrieval metrics like _mean reciprocal rank_,
  _precision_ or _discounted cumulative gain_.
  
  experimental[The ranking evaluation API is new and may change in non-backwards compatible ways in the future, even on minor versions updates.]
  
  [float]
  === Overview
  
  
negative.code: [[search-rank-eval]]
  == Ranking Evaluation API
  
  experimental[The ranking evaluation API is experimental and may be changed or removed completely in a future release,
  as well as change in non-backwards compatible ways on minor versions updates. Elastic will take a best effort 
  approach to fix any issues, but experimental features are not subject to the support SLA of official GA features.]
  
  The ranking evaluation API allows to evaluate the quality of ranked search
  results over a set of typical search queries. Given this set of queries and a
  