anchor.diff:  
   Array of failures if there were any unrecoverable errors during the process. If
   this is non-empty then the request aborted because of those failures.
  -Delete-by-query is implemented using batches and any failure causes the entire
  +Delete by query is implemented using batches, and any failure causes the entire
   process to abort but all failures in the current batch are collected into the
   array. You can use the `conflicts` option to prevent reindex from aborting on
   version conflicts.
  
positive.code: `noops`::
  
  This field is always equal to zero for delete by query. It only exists
  so that delete by query, update by query and reindex APIs return responses
   with the same structure.
  
  `retries`::
  
  The number of retries attempted by delete by query. `bulk` is the number
  of bulk actions retried and `search` is the number of search actions retried.
  
  `throttled_millis`::
  
  
negative.code: are distributed proportionally to each sub-request. Combine that with the point
  above about distribution being uneven and you should conclude that the using
  `size` with `slices` might not result in exactly `size` documents being
  deleted.
  * Each sub-request gets a slightly different snapshot of the source index
  though these are all taken at approximately the same time.
  
  [float]
  