anchor.diff:  --------------------------------------------------
   {
       "sort" : [
  -        { "post_date" : {"order" : "asc"} },
  +        { "post_date" : {"order" : "asc"}},
           "user",
           { "name" : "desc" },
           { "age" : "desc" },
  
positive.code: 
  Elasticsearch supports sorting by array or multi-valued fields. The `mode` option
  controls what array value is picked for sorting the document it belongs
  to. The `mode` option can have the following values: 
  
  [horizontal]
  `min`:: Pick the lowest value. 
  `max`:: Pick the highest value.
  `sum`:: Use the sum of all values as sort value. Only applicable for
          number based array fields. 
  `avg`:: Use the average of all values as sort value. Only applicable
          for number based array fields.
  
  
negative.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). For example:
  
  [source,js]
  