anchor.diff:  
   There are a number of options for the `field_value_factor` function:
   
  -[cols="<,<",options="header",]
  -|=======================================================================
  -| Parameter |Description
  -|`field` |Field to be extracted from the document.
  -|`factor` |Optional factor to multiply the field value with, defaults to 1.
  -|`modifier` |Modifier to apply to the field value, can be one of: `none`, `log`,
  - `log1p`, `log2p`, `ln`, `ln1p`, `ln2p`, `square`, `sqrt`, or `reciprocal`.
  - Defaults to `none`.
  -|`missing` |Value used if the document doesn't have that field. The modifier
  -and factor are still applied to it as though it were read from the document.
  -|=======================================================================
  +[horizontal]
  +`field`::
  +
  +    Field to be extracted from the document.
  +
  +`factor`::
  +
  +    Optional factor to multiply the field value with, defaults to `1`.
  +
  +`modifier`::
  +
  +    Modifier to apply to the field value, can be one of: `none`, `log`,
  +    `log1p`, `log2p`, `ln`, `ln1p`, `ln2p`, `square`, `sqrt`, or `reciprocal`.
  +    Defaults to `none`.
  +
  +`missing`::
  +
  +    Value used if the document doesn't have that field. The modifier
  +    and factor are still applied to it as though it were read from the document.
  +
   
   Keep in mind that taking the log() of 0, or the square root of a negative number
   is an illegal operation, and an exception will be thrown. Be sure to limit the
   values of the field with a range filter to avoid this, or use `log1p` and
   `ln1p`.
   
  -===== Decay functions
  +[[function-decay]]
  +==== Decay functions
   
   Decay functions score a document with a function that decays depending
   on the distance of a numeric field value of the document from a user
  
positive.code: score of the query is multiplied with the result of the script scoring. If
  you wish to inhibit this, set `"boost_mode": "replace"`
  
  ===== Weight
  
  The `weight` score allows you to multiply the score by the provided
  `weight`. This can sometimes be desired since boost value set on
  
negative.code: `min`::         min of query score and function score
  
  By default, modifying the score does not change which documents match. To exclude
  documents that do not meet a certain score threshold the `min_score` parameter can be set to the desired score threshold.
  
  [[score-functions]]
  ==== Score functions
  
  The `function_score` query provides several types of score functions:
  
  * <<function-script-score,`script_score`>>
  * <<function-weight,`weight`>>
  * <<function-random,`random_score`>>
  * <<function-field-value-factor,`field_value_factor`>>
  * <<function-decay,decay functions>>: `gauss`, `linear`, `exp`
  
  [[function-script-score]]
  ==== Script score
  
  The `script_score` function allows you to wrap another query and customize
  the scoring of it optionally with a computation derived from other numeric
  