anchor.diff:  `ignore_unmapped`::
   
       Indicates if the unmapped field should be treated as a missing value. Setting it to `true` is equivalent to specifying
  -    an `unmapped_type` in the field sort. The default is `false` (unmapped field are causing the search to fail).
  +    an `unmapped_type` in the field sort. The default is `false` (unmapped field cause the search to fail).
   
   NOTE: geo distance sorting does not support configurable missing values: the
   distance will always be considered equal to +Infinity+ when a document does not
  
positive.code: ==== Missing Values
  
  The `missing` parameter specifies how docs which are missing
  the field should be treated: The `missing` value can be
  set to `_last`, `_first`, or a custom value (that
  will be used for missing docs as the sort value).
  The default is `_last`.
  
negative.code: [[search-request-sort]]
  === Sort
  
  Allows you to add one or more sorts on specific fields. Each sort can be
  reversed as well. The sort is defined on a per field level, with special
  field name for `_score` to sort by score, and `_doc` to sort by index order.
  
  